From 1d024908c128efd6fc3011445ae430d2502f975d Mon Sep 17 00:00:00 2001 From: Mario Kahlhofer Date: Thu, 30 Nov 2023 21:03:53 +0100 Subject: [PATCH] Rework course to be aligned with the JKU lecture (up to OOP I) --- slides/content/m00_intro.md | 12 + slides/content/m03_syntax_primer.md | 6 +- slides/content/m04_data_types.md | 39 +- slides/content/m05_collections.md | 106 +--- slides/content/m07_examples.md | 53 +- slides/content/m08_functions.md | 77 +-- slides/content/m09_classes.md | 186 +------ snippets/java/M03_MaximumValue.java | 8 +- snippets/java/M04_StringConcatenation.java | 11 - snippets/java/M04_StringConversion.java | 4 +- snippets/java/M07_BasicControlFlow.java | 10 +- .../java/M07_EnumeratingOverElements.java | 4 +- .../java/M07_IteratingElementsByIndex.java | 4 +- .../java/M07_IteratingElementsByValue.java | 4 +- snippets/java/M07_PriceTax.java | 14 +- snippets/java/M07_SumOfAllDigits.java | 12 +- snippets/java/M08_PassByObjectReference.java | 21 - snippets/java/M08_RectangleFunctions.java | 10 +- snippets/java/M09_PassengersProgram.java | 25 +- snippets/java/M09_ShapesProgram.java | 41 -- snippets/java/inout/In.java | 475 ++++++++++++++++++ snippets/java/inout/Out.java | 217 ++++++++ snippets/python/m04_string_concatenation.py | 8 - snippets/python/m05_dict_operations.py | 20 - snippets/python/m05_set_arithmetic.py | 10 - snippets/python/m05_set_operations.py | 14 - snippets/python/m07_price_tax.py | 5 +- .../python/m08_pass_by_object_reference.py | 15 - snippets/python/m09_passengers_program.py | 14 +- snippets/python/m09_shapes_duck_typing.py | 19 - snippets/python/m09_shapes_program.py | 24 - 31 files changed, 824 insertions(+), 644 deletions(-) delete mode 100644 snippets/java/M04_StringConcatenation.java delete mode 100644 snippets/java/M08_PassByObjectReference.java delete mode 100644 snippets/java/M09_ShapesProgram.java create mode 100644 snippets/java/inout/In.java create mode 100644 snippets/java/inout/Out.java delete mode 100644 snippets/python/m04_string_concatenation.py delete mode 100644 snippets/python/m05_dict_operations.py delete mode 100644 snippets/python/m05_set_arithmetic.py delete mode 100644 snippets/python/m05_set_operations.py delete mode 100644 snippets/python/m08_pass_by_object_reference.py delete mode 100644 snippets/python/m09_shapes_duck_typing.py delete mode 100644 snippets/python/m09_shapes_program.py diff --git a/slides/content/m00_intro.md b/slides/content/m00_intro.md index dedba89..c5690e4 100644 --- a/slides/content/m00_intro.md +++ b/slides/content/m00_intro.md @@ -29,6 +29,18 @@ - [Libraries](#-libraries) - [Zen of Python](#-zen-of-python) +
+ +### 🏫 Today: JKU Agenda + +The online resources have a little bit more content than today's session: + +- More on Collections: Dictionaries and Sets +- More on Classes: Static Methods, Interfaces, and Duck-Typing +- String Concatenation & Function Passing Behavior + +
+ --- diff --git a/slides/content/m03_syntax_primer.md b/slides/content/m03_syntax_primer.md index 5fde7ea..9c6dd63 100644 --- a/slides/content/m03_syntax_primer.md +++ b/slides/content/m03_syntax_primer.md @@ -9,9 +9,9 @@ ```java // ./java/M03_MaximumValue.java#L5-L15 -List numbers = Arrays.asList(1, -10, 0, -5, -1000, 100, 7); +int[] numbers = {1, -10, 0, -5, -1000, 100, 7}; -int maximum = numbers.get(0); +int maximum = numbers[0]; for (int number : numbers) { if (number > maximum) { @@ -19,7 +19,7 @@ for (int number : numbers) { } } -System.out.println("The maximum value is " + maximum); +Out.println("The maximum value is " + maximum); ``` ```py diff --git a/slides/content/m04_data_types.md b/slides/content/m04_data_types.md index d7a7f48..82c76c4 100644 --- a/slides/content/m04_data_types.md +++ b/slides/content/m04_data_types.md @@ -154,10 +154,10 @@ As seen in the example, if you concatenate a string with a non-string, you even
```java -// ./java/M04_StringConversion.java#L3-L4 +// ./java/M04_StringConversion.java#L5-L6 int num = 42; -System.out.println("The number is " + num); +Out.println("The number is " + num); ``` ```py @@ -180,41 +180,6 @@ print("The number is", num) --- -### String Concatenation - -Use `str.join()` in Python to concatenate a large number of strings. \* - -
- -```java -// ./java/M04_StringConcatenation.java#L3-L8 - -String a = "How"; -String b = "to"; -String c = "concatenate"; -String d = "strings"; - -String result = String.join(" ", a, b, c, d); -``` - -```py -# ./python/m04_string_concatenation.py#L1-L7 - -a = "How" -b = "to" -c = "concatenate" -d = "strings" - -# we learn more about lists in the next modules ... -result = " ".join([a, b, c, d]) -``` - -
- -\* The equivalent of a [`StringBuilder`](https://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html) in Java would be [`io.StringIO`](https://docs.python.org/3.9/library/io.html#io.StringIO) in Python. - ---- - ## Boolean Types ```py diff --git a/slides/content/m05_collections.md b/slides/content/m05_collections.md index c39ec5d..9bcbe98 100644 --- a/slides/content/m05_collections.md +++ b/slides/content/m05_collections.md @@ -7,10 +7,18 @@ We will only look into a few collection types of Python. Find them all at [docs.python.org/3/library/stdtypes.html](https://docs.python.org/3/library/stdtypes.html) -- **Lists and arrays** in Java ➡ are just `list` in Python (but, there is also `tuple`) +Python has no **arrays**, instead we need to use the **dynamic datastructure `list`** in Python. + +
+ +There are more collection types that you will learn later this semester: + +- **Lists** in Java ➡ are `list` in Python (but, there is also `tuple`) - **Maps** in Java ➡ are `dict` in Python - **Sets** in Java ➡ are also `set` in Python +
+ --- ## Lists 1/2 @@ -144,99 +152,3 @@ print(name, age) - Actually, whenever you use a comma `,` in such contexts, a `tuple` is used implicitly.
- ---- - -## Dictionaries - -Dictionaries map keys to values. - -```py [|3-10|13-15|17-19|21-22|] -# ./python/m05_dict_operations.py - -grades = { - "math": 2, - "programming": 1, - "literature": 3 -} - -# alternative syntax -grades = dict(math=2, programming=1, literature=3) - - -grades["math"] # get elements by key -grades["math"] = 5 # set elements by key -grades["electronics"] = 4 # add a new element - -# remove an element (will raise an error if the key does not exist) -if "math" in grades: - del grades["math"] - -grades.keys() # get all the keys as a list -grades.values() # get all the values as a list - -``` - ---- - -## Sets 1/2 - -Sets hold multiple elements, without duplicates, but also without order. - -```py [|3|5-6|8|10-12|] -# ./python/m05_set_operations.py#L1-L10 - -numbers = {1, 1, 2, 3, 5} # notice how the '1' is only appended once after all - -numbers.add(7) # add new elements -numbers.add(1) # add elements that already exist (no effect) - -1 in numbers # check for existence (much faster than with lists) - -# remove elements (will raise an error if the element does not exist) -if 2 in numbers: - numbers.remove(2) -``` - -
- -💡 **You can NOT retrieve elements by index from a set!** - -```py -# numbers[0] -# 💥 TypeError: 'set' object is not subscriptable -``` - -You must iterate over them or convert the set to a list with `list(elements)` - -```py -# ./python/m05_set_operations.py#L12-L14 - -# iterate over set elements -for val in numbers: - print(val) -``` - -
- ---- - -## Sets 2/2: Set Arithmetic - -Sets are handy when you want to apply operations from set theory. - -```py -# ./python/m05_set_arithmetic.py - -a = {1, 2, 3, 4, 5} -b = {4, 5, 6, 7, 8} - -print("a | b =", a | b) # union -print("a & b =", a & b) # intersection -print("a - b =", a - b) # difference - -# > a | b = {1, 2, 3, 4, 5, 6, 7, 8} -# > a & b = {4, 5} -# > a - b = {1, 2, 3} - -``` diff --git a/slides/content/m07_examples.md b/slides/content/m07_examples.md index 1431d0a..38b9671 100644 --- a/slides/content/m07_examples.md +++ b/slides/content/m07_examples.md @@ -9,22 +9,22 @@
```java -// ./java/M07_BasicControlFlow.java#L3-L17 +// ./java/M07_BasicControlFlow.java#L5-L19 int x = 0; switch (x) { case 0: - System.out.println("The value is 0"); + Out.println("The value is 0"); break; case 1: - System.out.println("The value is 1"); + Out.println("The value is 1"); break; case 2: - System.out.println("The value is 2"); + Out.println("The value is 2"); break; default: - System.out.println("The value is something else"); + Out.println("The value is something else"); } ``` @@ -63,12 +63,10 @@ else:
```java -// ./java/M07_SumOfAllDigits.java#L6-L18 +// ./java/M07_SumOfAllDigits.java#L6-L16 -Scanner scanner = new Scanner(System.in); -System.out.print("Enter a number: "); -int n = scanner.nextInt(); -scanner.close(); +Out.print("Enter a number: "); +int n = In.readInt(); int digitSum = 0; @@ -77,7 +75,7 @@ while (n > 0) { n = n / 10; } -System.out.println("The digit sum is " + digitSum); +Out.println("The digit sum is " + digitSum); ``` ```py @@ -124,12 +122,12 @@ assert 5 // 2 == 2
```java -// ./java/M07_IteratingElementsByValue.java#L3-L7 +// ./java/M07_IteratingElementsByValue.java#L5-L9 String[] names = {"Lisa", "John", "Susan", "Alex"}; for (String name : names) { - System.out.println(name); + Out.println(name); } ``` @@ -160,12 +158,12 @@ for name in names:
```java -// ./java/M07_IteratingElementsByIndex.java#L3-L7 +// ./java/M07_IteratingElementsByIndex.java#L5-L9 int[] numbers = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}; for (int i = 5; i < 8; i++) { - System.out.println(numbers[i]); + Out.println(numbers[i]); } ``` @@ -333,13 +331,13 @@ numbers.sort(reverse=True)
```java -// ./java/M07_EnumeratingOverElements.java#L3-L9 +// ./java/M07_EnumeratingOverElements.java#L5-L11 String[] names = {"Lisa", "John", "Susan", "Alex"}; int i = 0; while (i < names.length) { - System.out.println(i + " " + names[i]); + Out.println(i + " " + names[i]); i++; } ``` @@ -371,19 +369,17 @@ for i, name in enumerate(names):
```java -// ./java/M07_PriceTax.java#L5-L16 +// ./java/M07_PriceTax.java#L5-L14 -List prices = Arrays.asList(12.3, 5.2, 8.7, 1.2, 8.0); -List gross = new ArrayList(); +double[] prices = {12.3, 5.2, 8.7, 1.2, 8.0}; +double[] gross = new double[5]; -for (double price : prices) { - if (price > 8) { - gross.add(price * 1.2); - } +for (int i = 0; i < prices.length; i++) { + gross[i] = prices[i] * 1.2; } for (double price : gross) { - System.out.println(price); + Out.println(price); } ``` @@ -394,8 +390,7 @@ prices = [12.3, 5.2, 8.7, 1.2, 8.0] gross = [] for price in prices: - if price > 8: - gross.append(price * 1.2) + gross.append(price * 1.2) print(gross) @@ -414,8 +409,8 @@ List comprehensions map each value in a list to a new value and thus create a ne ```py # ./python/m07_price_tax.py#L11-L12 -prices = [12.3, 5.2, 8.7, 1.2, 8.0] -gross = [price * 1.2 for price in prices if price > 8] +gross = [price * 1.2 for price in prices] + ``` \* Python offers a lot of features for functional programming, like [`map`](https://docs.python.org/3/library/functions.html#map) / [`filter`](https://docs.python.org/3/library/functions.html#filter) / [`reduce`](https://docs.python.org/3/library/functools.html#functools.reduce) / [`zip`](https://docs.python.org/3/library/functions.html#zip) / [`all`](https://docs.python.org/3/library/functions.html#all) / [`any`](https://docs.python.org/3/library/functions.html#any) / ... diff --git a/slides/content/m08_functions.md b/slides/content/m08_functions.md index 8543a46..d9c6627 100644 --- a/slides/content/m08_functions.md +++ b/slides/content/m08_functions.md @@ -7,7 +7,7 @@
```java -// ./java/M08_RectangleFunctions.java#L2-L16 +// ./java/M08_RectangleFunctions.java#L4-L18 static double area(double a, double b) { return a * b; @@ -18,11 +18,11 @@ static boolean isSquare(double a, double b) { } public static void main(String[] args) { - System.out.println("area(1, 5) = " + area(1, 5)); - System.out.println("area(1.5, 2.3) = " + area(1.5, 2.3)); + Out.println("area(1, 5) = " + area(1, 5)); + Out.println("area(1.5, 2.3) = " + area(1.5, 2.3)); - System.out.println("isSquare(1, 5) = " + isSquare(1, 5)); - System.out.println("isSquare(5, 5) = " + isSquare(5, 5)); + Out.println("isSquare(1, 5) = " + isSquare(1, 5)); + Out.println("isSquare(5, 5) = " + isSquare(5, 5)); } ``` @@ -58,73 +58,6 @@ print("is_square(5, 5) =", is_square(5, 5)) --- -## Pass by "Object Reference" / "Assignment" - -In a nutshell, Python has the same passing behavior as Java - although, Python lacks [**primitive types**](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html). - -
- -```java [|3-9|12-18|] -// ./java/M08_PassByObjectReference.java#L4-L20 - -static void replace(List numbers) { - numbers = Arrays.asList(42, 43, 44); -} - -static void append(List numbers) { - numbers.add(42); -} - -public static void main(String[] args) { - List oneTwoThree = new LinkedList<>(Arrays.asList(1, 2, 3)); - - replace(oneTwoThree); - System.out.println(Arrays.toString(oneTwoThree.toArray())); - - append(oneTwoThree); - System.out.println(Arrays.toString(oneTwoThree.toArray())); -} -``` - -```py [|3-8|11-17|] -# ./python/m08_pass_by_object_reference.py - -def replace(numbers): - numbers = [42, 43, 44] - - -def append(numbers): - numbers.append(42) - - -one_two_three = [1, 2, 3] - -replace(one_two_three) -print(one_two_three) # > [1, 2, 3] - -append(one_two_three) -print(one_two_three) # > [1, 2, 3, 42] - -``` - -
- -
- -**Arguments are ALWAYS passed by-value**, in Java and also in Python. -When your argument is an object, the reference to that object is passed. - -- In Java, when you pass a primitive type like `int`, the value is copied. -- Python has NO primitives. If you pass an `int`, the object reference is passed and NO data is copied. - But, since `int` is [**immutable**](https://docs.python.org/3/reference/datamodel.html), you can't change the value of the original object either. \* - -\* From here on, things get complicated. Learn more about the technical details by [Robert Heaton. 2014. "Is Python pass-by-reference or pass-by-value?"](https://robertheaton.com/2014/02/09/pythons-pass-by-object-reference-as-explained-by-philip-k-dick/)
and [Sreejith Kesavan. 2012. "Understanding Python Variables and Memory Management"](http://foobarnbaz.com/2012/07/08/understanding-python-variables/). - - -
- ---- - ## What else is different with Python functions? 1/3
diff --git a/slides/content/m09_classes.md b/slides/content/m09_classes.md index 292b0a8..4a8d979 100644 --- a/slides/content/m09_classes.md +++ b/slides/content/m09_classes.md @@ -9,7 +9,7 @@ Python is object-oriented, but follows a more lean approach towards classes.
```java -// ./java/M09_PassengersProgram.java#L3-L40 +// ./java/M09_PassengersProgram.java#L4-L37 class Passenger { @@ -22,28 +22,24 @@ class Passenger { } void display() { - System.out.printf("%s %s %n", firstName, lastName); + Out.println(firstName + " " + lastName); } +} - static Passenger fromInput() { - Scanner scanner = new Scanner(System.in); - - System.out.print("Enter first name: "); - String firstName = scanner.nextLine(); - System.out.print("Enter last name: "); - String lastName = scanner.nextLine(); +class PassengersProgram { - scanner.close(); + static Passenger createPassengerFromInput() { + Out.print("Enter first name: "); + String firstName = In.readLine(); + Out.print("Enter last name: "); + String lastName = In.readLine(); return new Passenger(firstName, lastName); } -} - -class PassengersProgram { public static void main(String[] args) { Passenger lisa = new Passenger("Lisa", "Ha"); - Passenger user = Passenger.fromInput(); + Passenger user = createPassengerFromInput(); lisa.display(); user.display(); @@ -51,7 +47,7 @@ class PassengersProgram { } ``` -```py [|3|4-6|8-9|11-16|20-24|19|] +```py [|3|4-6|8-9|12-16|19-24|19|] # ./python/m09_passengers_program.py class Passenger: @@ -60,19 +56,19 @@ class Passenger: self.last_name = last_name def display(self): - print(f"Passenger: {self.first_name} {self.last_name}") + print(self.first_name + " " + self.last_name) - @staticmethod - def from_input(): - first_name = input("Enter first name: ") - last_name = input("Enter last name: ") - return Passenger(first_name, last_name) +def create_passenger_from_input(): + first_name = input("Enter first name: ") + last_name = input("Enter last name: ") + + return Passenger(first_name, last_name) if __name__ == "__main__": lisa = Passenger("Lisa", "Ha") - user = Passenger.from_input() + user = create_passenger_from_input() lisa.display() user.display() @@ -106,155 +102,9 @@ if __name__ == "__main__":
-#### Static methods - -- A **static method** needs the `@staticmethod` [**decorator**](https://docs.python.org/3/glossary.html#term-decorator) and omits the `self` parameter -- A static method just means that it won't access any class properties - -
-
- #### Instantiation - Creating a new object works similar, but you omit the `new` keyword - The `main` method in Python is actually a condition - we will learn more in the next modules
- ---- - -## Informal Interfaces - -
- -```java -// ./java/M09_ShapesProgram.java - -interface Shape { - double area(); -} - -class Circle implements Shape { - - final double radius; - - Circle(double radius) { - this.radius = radius; - } - - @Override - public double area() { - return 3.14159 * radius * radius; - } -} - -class Square implements Shape { - - final double length; - - Square(double length) { - this.length = length; - } - - @Override - public double area() { - return length * length; - } -} - -class ShapesProgram { - - public static void main(String[] args) { - Shape[] shapes = { new Circle(5), new Square(10) }; - for (Shape shape : shapes) { - System.out.println(shape.area()); - } - } -} - -``` - -```py [|3-5|8-13|16-21|24-26|] -# ./python/m09_shapes_program.py - -class Shape: - def area(self): - pass - - -class Circle(Shape): - def __init__(self, radius): - self.radius = radius - - def area(self): - return 3.14159 * self.radius * self.radius - - -class Square(Shape): - def __init__(self, length): - self.length = length - - def area(self): - return self.length * self.length - - -shapes = [Circle(5), Square(10)] -for shape in shapes: - print(shape.area()) - -``` - -
- -
- -### What do we notice here? - -- There is no `interface` type in Python, instead we use a normal `class` and inhert from it -- Methods are overridden without an explicit annotation - they are always replaced -- No type checks are enforced by Python, try removing `Shape` or renaming the `area()` method ... - -
- ---- - -## Duck-Typing - -Since there is NO type-checking at compile-time, we may also solely rely on [**duck-typing**](https://docs.python.org/3/glossary.html#term-duck-typing). -An `AttributeError` is thrown at runtime, if the method you are calling wouldn't exist. \* - -```py [|3-16|19-21|21|] -# ./python/m09_shapes_duck_typing.py - -class Circle: - def __init__(self, radius): - self.radius = radius - - def area(self): - return 3.14159 * self.radius * self.radius - - -class Square: - def __init__(self, length): - self.length = length - - def area(self): - return self.length * self.length - - -shapes = [Circle(5), Square(10)] -for shape in shapes: - print(shape.area()) - -``` - -
- -### But, how can I have a "real" interfaces and inheritance in Python? - -- Use abstract classes via the [**`abc` module**](https://docs.python.org/3/library/abc.html) -- Learn more about formal interfaces at [realpython.com/python-interface](https://realpython.com/python-interface/) - -
- -\* Look into [**type hints**](https://docs.python.org/3/library/typing.html) to have better type-checking at runtime and even before you run your code. diff --git a/snippets/java/M03_MaximumValue.java b/snippets/java/M03_MaximumValue.java index e794d34..34405cc 100644 --- a/snippets/java/M03_MaximumValue.java +++ b/snippets/java/M03_MaximumValue.java @@ -1,10 +1,10 @@ -import java.util.*; +import inout.Out; class MaximumValue { public static void main(String[] args) { - List numbers = Arrays.asList(1, -10, 0, -5, -1000, 100, 7); + int[] numbers = {1, -10, 0, -5, -1000, 100, 7}; - int maximum = numbers.get(0); + int maximum = numbers[0]; for (int number : numbers) { if (number > maximum) { @@ -12,6 +12,6 @@ public static void main(String[] args) { } } - System.out.println("The maximum value is " + maximum); + Out.println("The maximum value is " + maximum); } } diff --git a/snippets/java/M04_StringConcatenation.java b/snippets/java/M04_StringConcatenation.java deleted file mode 100644 index 5c36a29..0000000 --- a/snippets/java/M04_StringConcatenation.java +++ /dev/null @@ -1,11 +0,0 @@ -class StringConcatenation { - public static void main(String[] args) { - String a = "How"; - String b = "to"; - String c = "concatenate"; - String d = "strings"; - - String result = String.join(" ", a, b, c, d); - System.out.println(result); - } -} diff --git a/snippets/java/M04_StringConversion.java b/snippets/java/M04_StringConversion.java index 69d124f..0ff2a52 100644 --- a/snippets/java/M04_StringConversion.java +++ b/snippets/java/M04_StringConversion.java @@ -1,6 +1,8 @@ +import inout.Out; + class StringConversion { public static void main(String[] args) { int num = 42; - System.out.println("The number is " + num); + Out.println("The number is " + num); } } diff --git a/snippets/java/M07_BasicControlFlow.java b/snippets/java/M07_BasicControlFlow.java index c1f976b..208c589 100644 --- a/snippets/java/M07_BasicControlFlow.java +++ b/snippets/java/M07_BasicControlFlow.java @@ -1,19 +1,21 @@ +import inout.Out; + class BasicControlFlow { public static void main(String[] args) { int x = 0; switch (x) { case 0: - System.out.println("The value is 0"); + Out.println("The value is 0"); break; case 1: - System.out.println("The value is 1"); + Out.println("The value is 1"); break; case 2: - System.out.println("The value is 2"); + Out.println("The value is 2"); break; default: - System.out.println("The value is something else"); + Out.println("The value is something else"); } } } diff --git a/snippets/java/M07_EnumeratingOverElements.java b/snippets/java/M07_EnumeratingOverElements.java index 44ab62f..d140615 100644 --- a/snippets/java/M07_EnumeratingOverElements.java +++ b/snippets/java/M07_EnumeratingOverElements.java @@ -1,10 +1,12 @@ +import inout.Out; + class EnumeratingOverElements { public static void main(String[] args) { String[] names = {"Lisa", "John", "Susan", "Alex"}; int i = 0; while (i < names.length) { - System.out.println(i + " " + names[i]); + Out.println(i + " " + names[i]); i++; } } diff --git a/snippets/java/M07_IteratingElementsByIndex.java b/snippets/java/M07_IteratingElementsByIndex.java index 0cb8063..106b6ce 100644 --- a/snippets/java/M07_IteratingElementsByIndex.java +++ b/snippets/java/M07_IteratingElementsByIndex.java @@ -1,9 +1,11 @@ +import inout.Out; + class IteratingElementsByIndex { public static void main(String[] args) { int[] numbers = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}; for (int i = 5; i < 8; i++) { - System.out.println(numbers[i]); + Out.println(numbers[i]); } } } diff --git a/snippets/java/M07_IteratingElementsByValue.java b/snippets/java/M07_IteratingElementsByValue.java index 04bbdec..fc754b1 100644 --- a/snippets/java/M07_IteratingElementsByValue.java +++ b/snippets/java/M07_IteratingElementsByValue.java @@ -1,9 +1,11 @@ +import inout.Out; + class IteratingElementsByValue { public static void main(String[] args) { String[] names = {"Lisa", "John", "Susan", "Alex"}; for (String name : names) { - System.out.println(name); + Out.println(name); } } } diff --git a/snippets/java/M07_PriceTax.java b/snippets/java/M07_PriceTax.java index fc5c61f..c6c7f6b 100644 --- a/snippets/java/M07_PriceTax.java +++ b/snippets/java/M07_PriceTax.java @@ -1,18 +1,16 @@ -import java.util.*; +import inout.Out; class PriceTax { public static void main(String[] args) { - List prices = Arrays.asList(12.3, 5.2, 8.7, 1.2, 8.0); - List gross = new ArrayList(); + double[] prices = {12.3, 5.2, 8.7, 1.2, 8.0}; + double[] gross = new double[5]; - for (double price : prices) { - if (price > 8) { - gross.add(price * 1.2); - } + for (int i = 0; i < prices.length; i++) { + gross[i] = prices[i] * 1.2; } for (double price : gross) { - System.out.println(price); + Out.println(price); } } } diff --git a/snippets/java/M07_SumOfAllDigits.java b/snippets/java/M07_SumOfAllDigits.java index 08a0341..04212d7 100644 --- a/snippets/java/M07_SumOfAllDigits.java +++ b/snippets/java/M07_SumOfAllDigits.java @@ -1,12 +1,10 @@ -import java.util.*; +import inout.In; +import inout.Out; class SumOfAllDigits { public static void main(String[] args) { - - Scanner scanner = new Scanner(System.in); - System.out.print("Enter a number: "); - int n = scanner.nextInt(); - scanner.close(); + Out.print("Enter a number: "); + int n = In.readInt(); int digitSum = 0; @@ -15,6 +13,6 @@ public static void main(String[] args) { n = n / 10; } - System.out.println("The digit sum is " + digitSum); + Out.println("The digit sum is " + digitSum); } } diff --git a/snippets/java/M08_PassByObjectReference.java b/snippets/java/M08_PassByObjectReference.java deleted file mode 100644 index 39cd62b..0000000 --- a/snippets/java/M08_PassByObjectReference.java +++ /dev/null @@ -1,21 +0,0 @@ -import java.util.*; - -class PassByObjectReference { - static void replace(List numbers) { - numbers = Arrays.asList(42, 43, 44); - } - - static void append(List numbers) { - numbers.add(42); - } - - public static void main(String[] args) { - List oneTwoThree = new LinkedList<>(Arrays.asList(1, 2, 3)); - - replace(oneTwoThree); - System.out.println(Arrays.toString(oneTwoThree.toArray())); - - append(oneTwoThree); - System.out.println(Arrays.toString(oneTwoThree.toArray())); - } -} diff --git a/snippets/java/M08_RectangleFunctions.java b/snippets/java/M08_RectangleFunctions.java index 56386fd..93a1b00 100644 --- a/snippets/java/M08_RectangleFunctions.java +++ b/snippets/java/M08_RectangleFunctions.java @@ -1,3 +1,5 @@ +import inout.Out; + class RectangleFunctions { static double area(double a, double b) { return a * b; @@ -8,10 +10,10 @@ static boolean isSquare(double a, double b) { } public static void main(String[] args) { - System.out.println("area(1, 5) = " + area(1, 5)); - System.out.println("area(1.5, 2.3) = " + area(1.5, 2.3)); + Out.println("area(1, 5) = " + area(1, 5)); + Out.println("area(1.5, 2.3) = " + area(1.5, 2.3)); - System.out.println("isSquare(1, 5) = " + isSquare(1, 5)); - System.out.println("isSquare(5, 5) = " + isSquare(5, 5)); + Out.println("isSquare(1, 5) = " + isSquare(1, 5)); + Out.println("isSquare(5, 5) = " + isSquare(5, 5)); } } diff --git a/snippets/java/M09_PassengersProgram.java b/snippets/java/M09_PassengersProgram.java index f197e09..337876b 100644 --- a/snippets/java/M09_PassengersProgram.java +++ b/snippets/java/M09_PassengersProgram.java @@ -1,4 +1,5 @@ -import java.util.*; +import inout.In; +import inout.Out; class Passenger { @@ -11,28 +12,24 @@ class Passenger { } void display() { - System.out.printf("%s %s %n", firstName, lastName); + Out.println(firstName + " " + lastName); } +} - static Passenger fromInput() { - Scanner scanner = new Scanner(System.in); - - System.out.print("Enter first name: "); - String firstName = scanner.nextLine(); - System.out.print("Enter last name: "); - String lastName = scanner.nextLine(); +class PassengersProgram { - scanner.close(); + static Passenger createPassengerFromInput() { + Out.print("Enter first name: "); + String firstName = In.readLine(); + Out.print("Enter last name: "); + String lastName = In.readLine(); return new Passenger(firstName, lastName); } -} - -class PassengersProgram { public static void main(String[] args) { Passenger lisa = new Passenger("Lisa", "Ha"); - Passenger user = Passenger.fromInput(); + Passenger user = createPassengerFromInput(); lisa.display(); user.display(); diff --git a/snippets/java/M09_ShapesProgram.java b/snippets/java/M09_ShapesProgram.java deleted file mode 100644 index 9ced0b0..0000000 --- a/snippets/java/M09_ShapesProgram.java +++ /dev/null @@ -1,41 +0,0 @@ -interface Shape { - double area(); -} - -class Circle implements Shape { - - final double radius; - - Circle(double radius) { - this.radius = radius; - } - - @Override - public double area() { - return 3.14159 * radius * radius; - } -} - -class Square implements Shape { - - final double length; - - Square(double length) { - this.length = length; - } - - @Override - public double area() { - return length * length; - } -} - -class ShapesProgram { - - public static void main(String[] args) { - Shape[] shapes = { new Circle(5), new Square(10) }; - for (Shape shape : shapes) { - System.out.println(shape.area()); - } - } -} diff --git a/snippets/java/inout/In.java b/snippets/java/inout/In.java new file mode 100644 index 0000000..eb89d29 --- /dev/null +++ b/snippets/java/inout/In.java @@ -0,0 +1,475 @@ +package inout; + +import java.io.*; +import java.util.LinkedList; + +/** + * Simple input from the keyboard or from a file. + *

Copyright (c) 2005 Hanspeter Moessenboeck, University of Linz

+ * + *

This class is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2, or (at your option) any + * later version.

+ * + *

This class is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY + * or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details.

+ *
+ * + *

This class allows reading formatted data either from the keyboard + * or from a file. It is intended to be used in an introductory + * programming course when classes, packages and exceptions are unknown + * at the beginning. To use it, simply copy In.class into the + * source file directory.

+ * + *

All input comes from the current input file, which is initially + * the keyboard. Opening a file with open() makes it the new current + * input file. Closing a file with close() switches back to the previous + * input file.

+ * + *

When reading from the keyboard, reading blocks until the user has entered + * a sequence of characters terminated by the return key. All methods read + * from this input buffer (including the terminating '\r' and '\n') until the + * buffer is fully consumed. When a method tries to read beyond the end + * of the buffer, it blocks again waiting for the next buffer.

+ * + *

End of file detection: When reading from the keyboard, eof can be + * signaled as ctrl-Z at the beginning of a new line. When reading from a file, + * eof occurs when an attempt is made to read beyond the end of the file. + * In either case In.done() returns false if the requested data could not + * be read because of eof.

+ */ +@SuppressWarnings("unused") +public class In { + + /** + * End of file indicator returned by read() or peek() when no more + * characters can be read. + */ + public static final char eof = '\uffff'; + + private static final int empty = '\ufffe'; + + private static final char eofChar = '\u0005'; // ctrl E + private static final LinkedList inputStack; + private static final LinkedList bufferStack; + private static final char[] LS; // line separator (eol) + + private static InputStream in; + private static boolean done; // true if recent operation was successful + private static char buf; // last read character + + private static char charAfterWhiteSpace() { + char c; + do c = read(); while (done && c <= ' '); + return c; + } + + private static String readDigits() { + StringBuilder b = new StringBuilder(); + char c = charAfterWhiteSpace(); + if (done && c == '-') { + b.append(c); + c = read(); + } + while (done && Character.isDigit(c)) { + b.append(c); + c = read(); + } + buf = c; + return b.toString(); + } + + private static String readFloatDigits() { + StringBuilder b = new StringBuilder(); + char c = charAfterWhiteSpace(); + if (done && (c == '+' || c == '-')) { + b.append(c); + c = read(); + } + while (done && Character.isDigit(c)) { + b.append(c); + c = read(); + } + if (done && (c == '.')) { + b.append(c); + c = read(); + while (done && Character.isDigit(c)) { + b.append(c); + c = read(); + } + } + if (done && (c == 'e' || c == 'E')) { + b.append(c); + c = read(); + if (done && (c == '+' || c == '-')) { + b.append(c); + c = read(); + } + while (done && Character.isDigit(c)) { + b.append(c); + c = read(); + } + } + buf = c; + return b.toString(); + } + + + /** + * Read a raw character (byte). + * If an attempt is made to read beyond the end of the file, + * eof is returned and done() yields false. Otherwise, the read byte + * is in the range 0..255. + */ + public static char read() { + char c; + if (buf != empty) { + c = buf; + if (buf != eof) buf = empty; + } else { + try { + c = (char) in.read(); + if (c >>> 5 == 6) { // UTF8 110xxxxx 10xxxxxx + char d = (char) in.read(); + c = (char) (((c % 32) << 6) + (d % 64)); + } + } catch (IOException e) { + done = false; + c = eof; + buf = eof; + } + } + if (c == eofChar && inputStack.size() == 0) { + c = eof; + buf = eof; + } + done = c != eof; + return c; + } + + /** + * Current available raw characters. + * In case of an error 0 is returned and done() yields false. + */ + public static int available() { + int avail; + try { + avail = in.available(); + } catch (IOException exc) { + avail = 0; + done = false; + } + return avail; + } + + /** + * Read a character, but skip white spaces (byte). + * If an attempt is made to read beyond the end of the file, + * eof is returned and done() yields false. Otherwise, the read byte + * is in the range 0..255. + */ + public static char readChar() { + return charAfterWhiteSpace(); + } + + /** + * Read a boolean value. + * This method skips white space and tries to read an identifier. If its value + * is "true" the method returns true otherwise false. If the identifier is neither + * "true" nor "false" done() yields false. + */ + public static boolean readBoolean() { + String s = readIdentifier(); + done = true; + if (s.equals("true")) { + return true; + } else { + done = s.equals("false"); + return false; + } + } + + /** + * Read an identifier. + * This method skips white space and tries to read an identifier starting + * with a letter and continuing with letters or digits. If a token of this + * structure could be read, it is returned otherwise the empty string is + * returned and done() yields false. + */ + public static String readIdentifier() { + StringBuilder b = new StringBuilder(); + char c = charAfterWhiteSpace(); + if (done && Character.isLetter(c)) { + b.append(c); + c = read(); + while (done && (Character.isLetter(c) || Character.isDigit(c))) { + b.append(c); + c = read(); + } + } + buf = c; + done = b.length() > 0; + return b.toString(); + } + + /** + * Read a word. + * This method skips white space and tries to read a word consisting of + * all characters up to the next white space or to the end of the file. + * If a token of this structure could be read, it is returned otherwise + * an empty string is returned and done() yields false. + */ + public static String readWord() { + StringBuilder b = new StringBuilder(); + char c = charAfterWhiteSpace(); + while (done && c > ' ') { + b.append(c); + c = read(); + } + buf = c; + done = b.length() > 0; + return b.toString(); + } + + /** + * Read a line of text. + * This method reads the rest of the current line (including eol) and + * returns it (excluding eol). A line may be empty. + */ + public static String readLine() { + StringBuilder b = new StringBuilder(); + char c = read(); + while (done && c != LS[0]) { + // Ignore '\r' on non-windows + if (c != '\r') { + b.append(c); + } + c = read(); + } + + int i = 0; + while (c == LS[i]) { + ++i; + if (i >= LS.length) { + break; + } + c = read(); + } + + if (i < LS.length) { + buf = c; + } else { + buf = empty; + } + if (b.length() > 0) { + done = true; + } + return b.toString(); + } + + /** + * Read the whole file. + * This method reads from the current position to the end of the + * file and returns its text in a single large string. done() yields + * always true. + */ + public static String readFile() { + StringBuilder b = new StringBuilder(); + char c = charAfterWhiteSpace(); + while (done) { + b.append(c); + c = read(); + } + buf = eof; + done = true; + return b.toString(); + } + + /** + * Read a quote-delimited string. + * This method skips white space and tries to read a string in the form "...". + * It can be used to read pieces of text that contain white space. + */ + public static String readString() { + StringBuilder b = new StringBuilder(); + char c = charAfterWhiteSpace(); + if (done && c == '"') { + c = read(); + while (done && c != '"') { + b.append(c); + c = read(); + } + if (c == '"') { + c = read(); + done = true; + } else { + done = false; + } + } else { + done = false; + } + buf = c; + return b.toString(); + } + + /** + * Read an integer. + * This method skips white space and tries to read an integer. If the + * text does not contain an integer or if the number is too big, the + * value 0 is returned and the subsequent call of done() yields false. + * An integer is a sequence of digits, possibly preceded by '-'. + */ + public static int readInt() { + String s = readDigits(); + try { + done = true; + return Integer.parseInt(s); + } catch (Exception e) { + done = false; + return 0; + } + } + + /** + * Read a long integer. + * This method skips white space and tries to read a long integer. If the + * text does not contain a number or if the number is too big, the + * value 0 is returned and the subsequent call of done() yields false. + * A long integer is a sequence of digits, possibly preceded by '-'. + */ + public static long readLong() { + String s = readDigits(); + try { + done = true; + return Long.parseLong(s); + } catch (Exception e) { + done = false; + return 0; + } + } + + /** + * Read a float value. + * This method skips white space and tries to read a float value. If the + * text does not contain a float value or if the number is not well-formed, + * the value 0f is returned and the subsequent call of done() yields false. + * A float value is as specified in the Java language description. It may + * be preceded by a '+' or a '-'. + */ + public static float readFloat() { + String s = readFloatDigits(); + try { + done = true; + return Float.parseFloat(s); + } catch (Exception e) { + done = false; + return 0f; + } + } + + /** + * Read a double value. + * This method skips white space and tries to read a double value. If the + * text does not contain a double value or if the number is not well-formed, + * the value 0.0 is returned and the subsequent call of done() yields false. + * A double value is as specified in the Java language description. It may + * be preceded by a '+' or a '-'. + */ + public static double readDouble() { + String s = readFloatDigits(); + try { + done = true; + return Double.parseDouble(s); + } catch (Exception e) { + done = false; + return 0.0; + } + } + + /** + * Peek at the next character. + * This method skips white space and returns the next character without removing + * it from the input stream. It can be used to find out, what token comes next + * in the input stream. + */ + public static char peek() { + char c = charAfterWhiteSpace(); + buf = c; + return c; + } + + /** + * Open a text file for reading + * The text file with the name fn is opened as the new current input + * file. When it is closed again, the previous input file is restored. + */ + public static void open(String fn) { + try { + InputStream s = new FileInputStream(fn); + bufferStack.add(buf); + inputStack.add(in); + in = s; + done = true; + } catch (FileNotFoundException e) { + done = false; + } + buf = empty; + } + + /** + * Close the current input file. + * The current input file is closed and the previous input file is + * restored. Closing the keyboard input has no effect but causes + * done() to yield false. + */ + public static void close() { + try { + if (inputStack.size() > 0) { + in.close(); + in = inputStack.removeLast(); + buf = bufferStack.removeLast(); + done = true; + } else { + done = false; + buf = empty; + } + } catch (IOException e) { + done = false; + buf = empty; + } + } + + /** + * Check if the previous operation was successful. + * This method returns true if the previous read operation was able + * to read a token of the requested structure. It can also be called + * after open() and close() to check if these operations were successful. + * If done() is called before any other operation it yields true. + */ + public static boolean done() { + return done; + } + + static { // initializer + done = true; + in = System.in; + buf = empty; + inputStack = new LinkedList<>(); + bufferStack = new LinkedList<>(); + String lineSeparator = System.getProperty("line.separator"); + if (lineSeparator == null) { + LS = new char[]{'\n'}; + } else { + char[] temp = lineSeparator.toCharArray(); + if (temp.length == 0) { + LS = new char[]{'\n'}; + } else { + LS = temp; + } + } + } + +} diff --git a/snippets/java/inout/Out.java b/snippets/java/inout/Out.java new file mode 100644 index 0000000..e94efe7 --- /dev/null +++ b/snippets/java/inout/Out.java @@ -0,0 +1,217 @@ +package inout; + +import java.io.*; + +/** + * Simple output to the console and to files. + *

Copyright (c) 2005 Hanspeter Moessenboeck, University of Linz

+ * + *

This class is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2, or (at your option) any + * later version.

+ * + *

This class is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY + * or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details.

+ *
+ * + *

This class allows printing formatted data either to the console + * or to a file. It is intended to be used in an introductory + * programming course when classes, packages and exceptions are unknown + * at the beginning. To use it, simply copy Out.class into the + * current directory.

+ * + *

All output goes to the current output file, which is initially + * the console. Opening a file with open() makes it the new current + * output file. Closing a file with close() switches back to the previous + * output file.

+ */ +@SuppressWarnings("unused") +public class Out { + + private static final PrintStream[] stack; + + private static PrintStream out; + private static int sp; + private static boolean done; + + /** + * Return true if the previous Out operation was + * successful, otherwise return false. + */ + public static boolean done() { + return done && !out.checkError(); + } + + /** + * Print the boolean value b either as "true" or "false". + */ + public static void print(boolean b) { + out.print(b); + } + + /** + * Print the character value c. + */ + public static void print(char s) { + out.print(s); + } + + /** + * Print the integer value i. + */ + public static void print(int i) { + out.print(i); + } + + /** + * Print the long value l. + */ + public static void print(long l) { + out.print(l); + } + + /** + * Print the float value f. + */ + public static void print(float f) { + out.print(f); + } + + /** + * Print the double value d. + */ + public static void print(double d) { + out.print(d); + } + + /** + * Print the character array a. + */ + public static void print(char[] a) { + out.print(a); + } + + /** + * Print the String s. + */ + public static void print(String s) { + out.print(s); + } + + /** + * Print the Object o as resulting from String.valueOf(o). + */ + public static void print(Object o) { + out.print(o); + } + + /** + * Terminate the current line by writing a line separator string. + * On Windows this is the character sequence '\r' and '\n' + */ + public static void println() { + out.println(); + } + + /** + * Print the boolean value b and terminate the line. + */ + public static void println(boolean b) { + out.println(b); + } + + /** + * Print the character value c and terminate the line. + */ + public static void println(char s) { + out.println(s); + } + + /** + * Print the integer value i and terminate the line. + */ + public static void println(int i) { + out.println(i); + } + + /** + * Print the long value l and terminate the line. + */ + public static void println(long l) { + out.println(l); + } + + /** + * Print the float value f and terminate the line. + */ + public static void println(float f) { + out.println(f); + } + + /** + * Print the double value d and terminate the line. + */ + public static void println(double d) { + out.println(d); + } + + /** + * Print the character array a and terminate the line. + */ + public static void println(char[] a) { + out.println(a); + } + + /** + * Print the String s and terminate the line. + */ + public static void println(String s) { + out.println(s); + } + + /** + * Print the Object o as resulting from String.valueOf(o) + * and terminate the line. + */ + public static void println(Object o) { + out.println(o); + } + + /** + * Open the file with the name fn as the current output file. + * All subsequent output goes to this file until it is closed. + * The old output file will be restored when the new output file is closed. + */ + public static void open(String fn) { + try { + PrintStream s = new PrintStream(new FileOutputStream(fn)); + stack[sp++] = out; + out = s; + } catch (Exception e) { + done = false; + } + } + + /** + * Close the current output file. + * The previous output file is restored and becomes the current output file. + */ + public static void close() { + out.flush(); + out.close(); + if (sp > 0) { + out = stack[--sp]; + } + } + + static { // initializer + done = true; + out = System.out; + stack = new PrintStream[8]; + sp = 0; + } + +} diff --git a/snippets/python/m04_string_concatenation.py b/snippets/python/m04_string_concatenation.py deleted file mode 100644 index 0376e73..0000000 --- a/snippets/python/m04_string_concatenation.py +++ /dev/null @@ -1,8 +0,0 @@ -a = "How" -b = "to" -c = "concatenate" -d = "strings" - -# we learn more about lists in the next modules ... -result = " ".join([a, b, c, d]) -print(result) diff --git a/snippets/python/m05_dict_operations.py b/snippets/python/m05_dict_operations.py deleted file mode 100644 index d7b9ed5..0000000 --- a/snippets/python/m05_dict_operations.py +++ /dev/null @@ -1,20 +0,0 @@ -grades = { - "math": 2, - "programming": 1, - "literature": 3 -} - -# alternative syntax -grades = dict(math=2, programming=1, literature=3) - - -grades["math"] # get elements by key -grades["math"] = 5 # set elements by key -grades["electronics"] = 4 # add a new element - -# remove an element (will raise an error if the key does not exist) -if "math" in grades: - del grades["math"] - -grades.keys() # get all the keys as a list -grades.values() # get all the values as a list diff --git a/snippets/python/m05_set_arithmetic.py b/snippets/python/m05_set_arithmetic.py deleted file mode 100644 index ddaa2ac..0000000 --- a/snippets/python/m05_set_arithmetic.py +++ /dev/null @@ -1,10 +0,0 @@ -a = {1, 2, 3, 4, 5} -b = {4, 5, 6, 7, 8} - -print("a | b =", a | b) # union -print("a & b =", a & b) # intersection -print("a - b =", a - b) # difference - -# > a | b = {1, 2, 3, 4, 5, 6, 7, 8} -# > a & b = {4, 5} -# > a - b = {1, 2, 3} diff --git a/snippets/python/m05_set_operations.py b/snippets/python/m05_set_operations.py deleted file mode 100644 index dfb71d8..0000000 --- a/snippets/python/m05_set_operations.py +++ /dev/null @@ -1,14 +0,0 @@ -numbers = {1, 1, 2, 3, 5} # notice how the '1' is only appended once after all - -numbers.add(7) # add new elements -numbers.add(1) # add elements that already exist (no effect) - -1 in numbers # check for existence (much faster than with lists) - -# remove elements (will raise an error if the element does not exist) -if 2 in numbers: - numbers.remove(2) - -# iterate over set elements -for val in numbers: - print(val) diff --git a/snippets/python/m07_price_tax.py b/snippets/python/m07_price_tax.py index 96b3684..424279f 100644 --- a/snippets/python/m07_price_tax.py +++ b/snippets/python/m07_price_tax.py @@ -2,13 +2,12 @@ gross = [] for price in prices: - if price > 8: - gross.append(price * 1.2) + gross.append(price * 1.2) print(gross) # or, with list comprehension prices = [12.3, 5.2, 8.7, 1.2, 8.0] -gross = [price * 1.2 for price in prices if price > 8] +gross = [price * 1.2 for price in prices] print(gross) diff --git a/snippets/python/m08_pass_by_object_reference.py b/snippets/python/m08_pass_by_object_reference.py deleted file mode 100644 index 75518dc..0000000 --- a/snippets/python/m08_pass_by_object_reference.py +++ /dev/null @@ -1,15 +0,0 @@ -def replace(numbers): - numbers = [42, 43, 44] - - -def append(numbers): - numbers.append(42) - - -one_two_three = [1, 2, 3] - -replace(one_two_three) -print(one_two_three) # > [1, 2, 3] - -append(one_two_three) -print(one_two_three) # > [1, 2, 3, 42] diff --git a/snippets/python/m09_passengers_program.py b/snippets/python/m09_passengers_program.py index 333ef5a..dcbbb19 100644 --- a/snippets/python/m09_passengers_program.py +++ b/snippets/python/m09_passengers_program.py @@ -4,19 +4,19 @@ def __init__(self, first_name, last_name): self.last_name = last_name def display(self): - print(f"Passenger: {self.first_name} {self.last_name}") + print(self.first_name + " " + self.last_name) - @staticmethod - def from_input(): - first_name = input("Enter first name: ") - last_name = input("Enter last name: ") - return Passenger(first_name, last_name) +def create_passenger_from_input(): + first_name = input("Enter first name: ") + last_name = input("Enter last name: ") + + return Passenger(first_name, last_name) if __name__ == "__main__": lisa = Passenger("Lisa", "Ha") - user = Passenger.from_input() + user = create_passenger_from_input() lisa.display() user.display() diff --git a/snippets/python/m09_shapes_duck_typing.py b/snippets/python/m09_shapes_duck_typing.py deleted file mode 100644 index 0cd9ee9..0000000 --- a/snippets/python/m09_shapes_duck_typing.py +++ /dev/null @@ -1,19 +0,0 @@ -class Circle: - def __init__(self, radius): - self.radius = radius - - def area(self): - return 3.14159 * self.radius * self.radius - - -class Square: - def __init__(self, length): - self.length = length - - def area(self): - return self.length * self.length - - -shapes = [Circle(5), Square(10)] -for shape in shapes: - print(shape.area()) diff --git a/snippets/python/m09_shapes_program.py b/snippets/python/m09_shapes_program.py deleted file mode 100644 index eca9423..0000000 --- a/snippets/python/m09_shapes_program.py +++ /dev/null @@ -1,24 +0,0 @@ -class Shape: - def area(self): - pass - - -class Circle(Shape): - def __init__(self, radius): - self.radius = radius - - def area(self): - return 3.14159 * self.radius * self.radius - - -class Square(Shape): - def __init__(self, length): - self.length = length - - def area(self): - return self.length * self.length - - -shapes = [Circle(5), Square(10)] -for shape in shapes: - print(shape.area())