files and modules

Akuli · Akuli · commit 2c0317f5b18b · 2016-09-26T20:38:48.000+03:00
diff --git a/README.md b/README.md
@@ -34,11 +34,12 @@ it.**
 9. [Handy stuff with strings](handy-stuff-strings.md)
 10. [Loops](loops.md)
 11. [Files](files.md)
+12. [Modules](modules.md)
+13. [Defining functions](defining-functions.md)
 
 Parts of this tutorial that aren't ready to be added to the rest of it
 yet:
 
-- [Defining functions](defining-functions.md)
 - [Classes](classes.md)
 
 Other things this tutorial comes with:
@@ -47,6 +48,7 @@ Other things this tutorial comes with:
 - [Contact me](contact-me.md)
 - [Setting up a text editor](editor-setup.md)
 - [Answers for the exercises](answers.md)
+- [The TODO list](TODO.md)
 
 I'm Akuli and I have written most of this tutorial, but the following
 people have helped me with it:
diff --git a/TODO.md b/TODO.md
@@ -6,51 +6,19 @@ This tutorial is not complete. It still needs:
     are needed for dict keys)
 - Explain `for a, b in thing` somewhere
 - **More exercises and examples everywhere!**
-- reading and writing files
-    - first of all: what are files, directories/folders and paths
-    - print(..., file=thefile), not thefile.write(...)
-    - show how to iterate over the file and .read() it
-    - why .rstrip('\n') instead of .strip()
-    - files remember their position, reading the same file object twice
-- modules
-    - just files and folders, have a look at Python's lib directory
-    - "batteries included" filosofy
-    - briefly introduce some of the most commonly used standard library
-        modules:
-        - math
-            - it's not a file, what is it?
-        - sys
-            - sys.exit() vs exit()
-        - time
-        - os, os.path, subprocess
-        - random
-        - webbrowser
-    - explain even more briefly and link to documentation/tutorials:
-        - configparser
-        - textwrap
-        - collections, itertools, functools
-        - traceback
-        - types
-        - warnings
-        - json
-    - link to third party modules:
-        - appdirs
-        - requests
 - Exceptions
 - explain bool(x) and why it matters
 - classes part 2
     - non-public `_variables`
     - singular inheritance, inheritance of built-in classes
     - using super
+- no classes part 3 with multiple inheritance, it's not something people need
 - quick overview of some of the most useful built-in functions and classes
     - range
     - zip
     - classmethod and staticmethod
-- iterables and iterators: something most Python programmers need to be aware of
-- classes part 3: multiple inheritance
-    - an advanced thing
-    - built-in classes don't use it
-    - diamond diagrams, why to use super()
+- iterables and iterators: something most Python programmers need to be
+    aware of
 - last chapter: "What should I do now?" links to other resources
     - GUI programming tutorials
         - easygui
@@ -60,3 +28,9 @@ This tutorial is not complete. It still needs:
     - a pygame tutorial
     - David Beazley's metaprogramming and other talks
     - a regex tutorial
+
+
+## Fix these
+
+- the chapter about installing python should mention that python 2 and 3
+    can be and often are installed at the same time
diff --git a/files.md b/files.md
@@ -5,7 +5,7 @@
 These are simple thing that many computer users already know, but I'll go
 through them just to make sure you know them also.
 
-#### Files
+### Files
 
 - Each file has a **name**, like `hello.py`, `mytext.txt` or
     `coolimage.png`. Usually the name ends with an **extension** that
@@ -17,13 +17,13 @@ through them just to make sure you know them also.
 - Files have **content** that consists of
     [8-bit bytes](https://www.youtube.com/watch?v=Dnd28lQHquU).
 
-#### Directories/folders
+### Directories/folders
 
 Directories are a way to group files. They also have a name and a location
 like files, but instead of containing data directly like files do they
 contain other files and directories.
 
-#### Paths
+### Paths
 
 Directories and files have a path, like `C:\Users\me\hello.py`. That just
 means that there's a folder called `C:`, and inside it there's a folder
@@ -178,7 +178,16 @@ It's also possible to read lines one by one. Files have a
 `readline()` method that reads the next line, and returns `''`
 if we're at the end of the file.
 
-**TODO:** example of readline()
+```py
+>>> with open('hello.txt', 'r') as f:
+...     first_line = f.readline()
+...     second_line = f.readline()
+... 
+>>> first_line
+'Hello one!\n'
+>>> second_line
+'Hello two!\n'
+```
 
 There's only one confusing thing about reading files. If you try
 to read it twice you'll find out that it only gets read once:
@@ -199,7 +208,10 @@ to read it twice you'll find out that it only gets read once:
 >>> 
 ```
 
-But if we open the file again, everything works.
+File objects remember their position. When we tried to read the
+file again it was already at the end, and there was nothing left
+to read. But if we open the file again, it's in the beginning
+again and everything works.
 
 ```py
 >>> first = []
@@ -247,7 +259,38 @@ use the `read()` method.
 >>> 
 ```
 
-**TODO:** Explain paths and \\.
+You can also open full paths, like `open('C:\\Users\\me', 'r')`.
+The reason why we need to use `\\` when we really mean `\` is that
+backslash has a special meaning. There are special characters like
+`\n`, and `\\` means an actual backslash.
+
+```py
+>>> print('C:\some\name')
+C:\some
+ame
+>>> print('C:\\some\\name')
+C:\some\name
+>>> 
+```
+
+Another way to create paths is to tell Python to escape them by
+adding an `r` to the beginning of the string. In this case the `r`
+is short for "raw", not "read".
+
+```py
+>>> r'C:\some\name' == 'C:\\some\\name'
+True
+>>> 
+```
+
+If you don't use Windows and your paths don't contain backslashes
+you don't need to double anything or use `r` in front of paths.
+
+```py
+>>> print('/some/name')
+/some/name
+>>> 
+```
 
 ## Example: File viewer
 
diff --git a/modules.md b/modules.md
