learning at 20190929

vodaka · vodaka · commit d9beaa0a9c8e · 2019-09-29T14:22:35.000+08:00
diff --git a/python3_programming_tricks/ch07/7-2.py b/python3_programming_tricks/ch07/7-2.py
@@ -0,0 +1,50 @@
+# 这里用两种方式定了palyer类，一种是palyer1,一种是palyer2
+
+
+class Player1:
+    def __init__(self, uid, name, level):
+        self.uid = uid
+        self.name = name
+        self.level = level
+
+
+class Player2:
+    __slots__ = ['uid', 'name', 'level'] # 类属性
+    def __init__():
+        self.uid = uid
+        self.name = name
+        self.level = level
+
+
+p1 = Player1('0001', 'Jim', 20)
+p2 = Player2('0001', 'Jim', 20)
+dir(p1)
+dir(p2)
+set(dir(p1)) - set(dir(p2))  # 主要浪费内存的地方是__dict__，其用于动态属性的维护
+p1.__dict__['z'] = 300 # 等同于p1.z = 300
+
+import sys
+
+sys.getsizeof(p1.__dict__) # 864 bytes
+sys.getsizeof(p1.name) # 52 bytes
+sys.getsizeof(p1.level) # 28 bytes
+sys.getsizeof(p1.uid) # 53 bytes
+
+# 为了避免内存的浪费，就关闭动态属性
+# p2.x = 1 # AttributeError
+
+# 测试
+
+import tracemalloc  # 跟踪内存使用
+
+tracemalloc.start()
+# start
+la = [Player1(1,2,3) for _ in range(100000)]
+#lb = [Player2(1,2,3) for _ in range(100000)]
+# end
+snapshot = tracemalloc.take_snapshot()
+#top_stats = snapshot.statistics('lineno')
+top_stats = snapshot.statistics('filename')
+for stat in top_stats[:10]: print(stat)
+
+
diff --git a/python3_programming_tricks/ch07/7-3.py b/python3_programming_tricks/ch07/7-3.py
@@ -0,0 +1,68 @@
+from sys import stdin, stdout
+import getpass
+import telnetlib
+from collections import deque
+
+class TelnetClient:
+    def __init__(self, host, port=23):
+        self.host = host
+        self.port = port
+
+    def connect(self):
+        self.tn = telnetlib.Telnet(self.host, self.port)
+        self.history = deque([])
+
+    def cleanip(self):
+        self.tn.close()
+        self.tn = None
+
+        with open('history.txt', 'a') as f:
+            f.writelienes(self.history)
+
+    def login(self):
+        # user
+        self.tn.read_until(b"login: ")
+        user = input("Enter your remote account: ")
+        self.tn.write(user.encode('utf8') + b'\n')
+
+        # password
+        self.tn.read_until(b'Password: ')
+        password = getpass.getpass()
+        self.tn.write(password.encode('utf8') + b'\n')
+        out = self.tn.read_until(b'$ ')
+        stdout.write(out.decode('utf8'))
+
+    def interact(self):
+        while True:
+            cmd = stdin.readline()
+            if not cmd:
+                break
+
+        self.history.append(cmd)
+        self.tn.write(cmd.encode('utf8'))
+        out = self.tn.read_until(b'$ ').decode('utf8')
+
+        stdout.write(out[len(cmd)+1:])
+        stdout.flush()
+
+
+client = TelnetClient('192.168.0.105')
+client.connect()
+client.login()
+client.interact()
+client.cleanup()
+
+# with上下文管理说明
+#with open('demo.txt', 'w') as f:
+#    f.write('abc')
+#    f.write('efef')
+#
+#f.close   # 返回True
+#
+#F = open('demo.txt', 'w')
+#f = F.__enter__()  # with上下文管理需要的方法，只不过此方法实现中返回的是F. 进入的时候调用此方法
+#f is F # 返回True
+#F.__exit__()  # 退出的时候调用此方法
+
+# 所以需要将上面代码中的connect , cleanup方法分别改成__enter__和__exit__方法
+
diff --git a/python3_programming_tricks/ch07/7-3_v2.py b/python3_programming_tricks/ch07/7-3_v2.py
@@ -0,0 +1,68 @@
+from sys import stdin, stdout
+import getpass
+import telnetlib
+from collections import deque
+
+class TelnetClient:
+    def __init__(self, host, port=23):
+        self.host = host
+        self.port = port
+
+#    def connect(self):
+#        self.tn = telnetlib.Telnet(self.host, self.port)
+#        self.history = deque([])
+    def __enter__(self):
+        self.tn = telnetlib.Telnet(self.host, self.port)
+        self.history = deque([])
+
+#    def cleanup(self):
+#        self.tn.close()
+#        self.tn = None
+#
+#        with open('history.txt', 'a') as f:
+#            f.writelienes(self.history)
+    def __exit_(self, exc_type, exc_value, exc_tb):
+        self.tn.close()
+        self.tn = None
+
+        with open('history.txt', 'a') as f:
+            f.writelienes(self.history)
+
+    def login(self):
+        # user
+        self.tn.read_until(b"login: ")
+        user = input("Enter your remote account: ")
+        self.tn.write(user.encode('utf8') + b'\n')
+
+        # password
+        self.tn.read_until(b'Password: ')
+        password = getpass.getpass()
+        self.tn.write(password.encode('utf8') + b'\n')
+        out = self.tn.read_until(b'$ ')
+        stdout.write(out.decode('utf8'))
+
+    def interact(self):
+        while True:
+            cmd = stdin.readline()
+            if not cmd:
+                break
+
+        self.history.append(cmd)
+        self.tn.write(cmd.encode('utf8'))
+        out = self.tn.read_until(b'$ ').decode('utf8')
+
+        stdout.write(out[len(cmd)+1:])
+        stdout.flush()
+
+
+#client = TelnetClient('192.168.0.105')
+#client.connect()
+#client.login()
+#client.interact()
+#client.cleanup()
+
+with TelnetClient('192.168.0.105') as client:
+    client.login()
+    client.interact()
+
+print('END')
diff --git a/python3_programming_tricks/ch07/7_class_and_object.md b/python3_programming_tricks/ch07/7_class_and_object.md
@@ -15,3 +15,31 @@ IntTuple([1, -1, 'abc', 6, ['x','y'],3]) => (1,6,3)
 **解决方案**
 
 继承内置tuple,并实现\_\_new\_\_.在其中修改实例化行为
+
+## 7.2 如何为创建大量实例节省内存
+
+**实际案例**
+
+在某网络游戏中，定义了玩家类Player(id, name, level, ...).每有一个在线玩家，在服务器程序内则有一个Player实例。
+当在线人数很多时，将产生大量实例。(如百万级)
+如何降低这些大量实例的内存开销？
+
+**解决方案**
+
+定义类的\_\_slots\_\_属性，声明实例有哪些属性(关闭动态绑定)
+
+## 7.3 如何让对象支持上下文管理
+
+**实际案例**
+
+我们实现了一个telnet客户端的类TelnetClient，调用实例的connect(),login(),interact()方法启动客户端与服务器交互，交互完毕后需要调用cleanup()方法，关闭已连接的socket，以及操作历史记录写入文件并关闭。
+能否让TelnetClient的实例支持上下文管理协议，从而替代手工调用cennect(), cleanup()方法。
+
+**解决方案**
+
+实现上下文管理协议，即实现类的\_\_enter\_\_,\_\_exit\_\_方法
+它们分别在with开始和结束时被调用
+
+
+
+
