Python：Python学习总结

1 # coding=utf-8
2
3 print "你好，世界。"

1 print 2**10

1 var = 1
2 print var
3
4 var = "段光伟"
5 print var

1 #获取用户输入
2 x = input("x:")
3 y = input("y:")
4
5 print x*y

1 def say_b():
2 print "b"

1 #1 + “1” 这行代码在Python中会报错。
2 print 1 + int("1")
3 print str(1) + "1"

1 #字符串
2 print '''' 段
3 光
4 伟'''
5 print r'C:\log.txt'
6 print 'C:\\log.txt'

1 seq = "0123456789"
2 print seq[0] #从0开始编码。
3 print seq[-1] #支持倒着数数，-1代表倒数第一。
4 print seq[1:5] #支持分片操作，seq[start:end]，start会包含在结果中，end不会包含在结果中。
5 print seq[7:] #seq[start:end]中的end可以省略。
6 print seq[-3:] #分片也支持负数。
7 print seq[:3] #seq[start:end]中的start也可以省略。
8 print seq[:] #全部省略会复制整个序列。
9 print seq[::2] #支持步长。
10 print seq[::-2] #支持负步长。
11 print seq[9:1:-1] #支持负步长。
12 print [1, 2, 3] + [4, 5, 6] # 序列支持相加，这解释了为啥字符串可以相加。
13 print [1, 2, 3] * 3 #序列支持相乘，这解释了为啥字符串可以相称。
14 print [None] * 10 #生成一个空序列。
15 print 1 in [1, 2, 3] #成员判断。

1 data = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
2
3 data[0] = "a" #修改元素。
4 print data
5 data[0] = 0
6
7 del data[10] #删除元素。
8 print data
9
10 del data[8:] #分片删除。
11 print data
12
13 data[8:] = [8, 9, 10] #分片赋值
14 print data

1 print (1, 2) #元祖以小括号形式声明。
2 print (1,) #一个元素的元祖。

1 print "% 10s" % "----"
2
3 print '''
4 %(title)s
5 %(body)s
6 ''' % {"title": "标题", "body": "内容"}

1 print {"title": "title", "body": "body"}
2 print dict(title = "title", body = "body")
3 print dict([("title", "title"), ("body", "body")])

1 dic = {"title": "title", "body": "body"};
2 print dic["title"]
3 del dic["title"]
4 print dic

1 print 'a', 'b' #print可以接受多个参数，参数的输出之间以空格相隔。
2 print 'a', #如果逗号之后没有参数，则不会换行。
3 print 'b'

1 x, y, z = 1, 2, 3
2 print x, y, z
3 (x, y, z) = (1, 2, 3)
4 print x, y, z
5 (x, y, z) = [1, 2, 3]
6 print x, y, z

1 #下面的输入全部返回False。
2 print(bool(None))
3 print(bool(()))
4 print(bool([]))
5 print(bool({}))
6 print(bool(""))
7 print(bool(0))
8
9 #虽然这些值在条件运算中会当做False，但是本身不等于False。
10 print(True and "")
11 print(not "")
12 print(False == "")
13 print(False == 0) #0除外，bool类型的内部表示就是int类型。

1 print(0 < 1 < 10)
2 print(0 < 1 and 1 < 10)
3 print(not(0 > 1 > 10))
4 print(not(0 > 1 or 1 > 10))

1 if(10 > 1):
2 print("10 > 1")
3 else:
4 print("不可能发生")

1 print("10 > 1" if 10 > 1 else "不可能发生")

1 #== 和 is的差别，==比较的是内容，is比较的是引用。
2 x = [1, 2, 3]
3 y = x
4 z = [1, 2, 3]
5 print(x == y)
6 print(x == z)
7 print(x is y)
8 print(x is z)

1 #for循环类似C#的foreach，注意for后面是没有括号的，python真是能简洁就尽量简洁。
2 for x in range(1, 10):
3 print(x)
4
5 for key in {"x":"xxx"}:
6 print(key)
7
8 for key, value in {"x":"xxx"}.items():
9 print(key, value)
10
11 for x, y, z in [["a", 1, "A"],["b", 2, "B"]]:
12 print(x, y, z)

1 #带索引的遍历
2 for index, value in enumerate(range(0, 10)):
3 print(index, value)
4
5 #好用的zip方法
6 for x, y in zip(range(1, 10), range(1, 10)):
7 print(x, y)
8
9 #循环中的的else子句
10 from math import sqrt
11 for item in range(99, 1, -1):
12 root = sqrt(item)
13 if(root == int(root)):
14 print(item)
15 break
16 else:
17 print("没有执行break语句。")

1 #pass、exec、eval
2 if(1 == 1):
3 pass
4
5 exec('print(x)', {"x": "abc"})
6 print(eval('x*2', {"x": 5}))

1 # 基本函数定义。
2 def func():
3 print("func")
4
5 func()
6
7 # 带返回值的函数。
8 def func_with_return():
9 return ("func_with_return")
10
11 print(func_with_return())
12
13 # 带多个返回值的函数。
14 def func_with_muti_return():
15 return ("func_with_muti_return", "func_with_muti_return")
16
17 print(func_with_muti_return())
18
19 # 位置参数
20 def func_with_parameters(x, y):
21 print(x, y)
22
23 func_with_parameters(1, 2)
24
25 # 收集多余的位置参数
26 def func_with_collection_rest_parameters(x, y, *rest):
27 print(x, y)
28 print(rest)
29
30 func_with_collection_rest_parameters(1, 2, 3, 4, 5)
31
32 #命名参数
33 def func_with_named_parameters(x, y, z):
34 print(x, y, z)
35
36 func_with_named_parameters(z = 1, y = 2, x = 3)
37
38 #默认值参数
39 def func_with_default_value_parameters(x, y, z = 3):
40 print(x, y, z)
41
42 func_with_default_value_parameters(y = 2, x = 1)
43
44 #收集命名参数
45 def func_with_collection_rest_naned_parameters(*args, **named_agrs):
46 print(args)
47 print(named_agrs)
48
49 func_with_collection_rest_naned_parameters(1, 2, 3, x = 4, y = 5, z = 6)
50
51 #集合扁平化
52 func_with_collection_rest_naned_parameters([1, 2, 3], {"x": 4, "y": 4, "z": 6}) #这会导致args[0]指向第一个实参，args[1]指向第二个实参。
53 func_with_collection_rest_naned_parameters(*[1, 2, 3], **{"x": 4, "y": 4, "z": 6}) #这里的执行相当于func_with_collection_rest_naned_parameters(1, 2, 3, x = 4, y = 5, z = 6)。

1 # coding=utf-8
2
3 # 只有函数执行才会开启一个作用域。
4 if(2 > 1):
5 x = 1
6
7 print(x) # 会输出1。
8
9
10 # 使用vars()函数可以访问当前作用域包含的变量。
11 x = 1
12 print(vars()["x"])
13
14 # 使用globals()函数可以访问全局作用域。
15 x = 1
16
17 def func():
18 print(globals()["x"])
19
20 func()
21
22 # 使用locals()函数可以访问局部作用域。
23 def func():
24 x = 2
25 print(locals()["x"])
26
27 func()
28
29 # 每个函数定义时都会记住所在的作用域。
30 # 函数执行的时候会开启一个新的作用域，函数内变量访问的规则是：先访问当前作用域，如果没有就访问函数定义时的作用域，递归直到全局作用域。
31 x = 1
32
33 def func():
34 y = 2
35 print(x, y) # 输出1 2
36
37 func()
38
39
40 # 变量赋值始终访问的是当前作用域。
41 x = 1
42
43 def func():
44 x = 2
45 y = 2
46 print(x, y) # 输出2 2
47
48 func()
49 print(x) #输出 1
50
51 # 局部变量会覆盖隐藏全局变量，想访问全局变量可以采用global关键字或globals()函数。
52 x = 1
53
54 def func():
55 global x
56 x = 2
57 y = 2
58 print(x, y) # 输出2 2
59
60 func()
61 print(x) #输出 2

1 # python支持闭包
2 def func(x):
3 def inner_func(y):
4 print(x + y)
5
6 return inner_func
7
8 inner_func = func(10)
9 inner_func(1)
10 inner_func(2)

1 #函数作为对象
2 def func(fn, arg):
3 fn(arg)
4
5 func(print, "hello")
6 func(lambda arg : print(arg), "hello")

1 # coding=utf-8
2
3 print __name__
4
5 def say_b():
6 print "b"

1 # coding=utf-8
2
3 import b
4 from b import *
5
6 print __name__
7
8 def say_a():
9 print "a"

1 # coding=utf-8
2
3 import a
4
5 print __name__
6
7 a.say_a();
8 a.say_b();
9 a.b.say_b()

1 b
2 a
3 __main__
4 a
5 b
6 b

1 # coding=utf-8
2
3 # 自定义异常
4 class HappyException(Exception):
5 pass
6
7 # 引发和捕获异常
8 try:
9 raise HappyException
10 except:
11 print("HappyException")
12
13 try:
14 raise HappyException()
15 except:
16 print("HappyException")
17
18 # 捕获多种异常
19 try:
20 raise HappyException
21 except (HappyException, TypeError):
22 print("HappyException")
23
24 # 重新引发异常
25 try:
26 try:
27 raise HappyException
28 except (HappyException, TypeError):
29 raise
30 except:
31 print("HappyException")
32
33 #访问异常实例
34 try:
35 raise HappyException("都是我的错")
36 except (HappyException, TypeError), e:
37 print(e)
38
39 #按类型捕获
40 try:
41 raise HappyException
42 except HappyException:
43 print("HappyException")
44 except TypeError:
45 print("TypeError")
46
47 #全面捕获
48 try:
49 raise HappyException
50 except:
51 print("HappyException")
52
53 #没有异常的else
54 try:
55 pass
56 except:
57 print("HappyException")
58 else:
59 print("没有异常")
60
61 #总会执行的final
62 try:
63 pass
64 except:
65 print("HappyException")
66 else:
67 print("没有异常")
68 finally:
69 print("总会执行")

1 # coding=utf-8
2
3 __metaclass__ = type
4
5 # 类型定义
6 # 实例方法必的第一个参数代表类型实例，类似其他语言的this。
7 class Animal:
8 name = "未知" # 属性定义。
9
10 def __init__(self, name): #构造方法定义。
11 self.name = name
12
13 def getName(self): # 实例方法定义。
14 return self.name
15
16 def setName(self, value):
17 self.name = value
18
19 print(Animal.name) # 未知
20 print(Animal.__dict__["name"]) # 未知
21
22 animal = Animal("狗狗")
23 print(animal.name) # 狗狗
24 print(animal.__dict__["name"]) # 狗狗
25 print(Animal.name) # 未知
26 print(Animal.__dict__["name"]) # 未知
27 print(animal.__class__.name) # 未知
28 print(animal.__class__.__dict__["name"]) # 未知

1 # 类型定义中的代码会执行，是一个独立的作用域。
2 class TestClass:
3 print("类型定义中") #类型定义中

1 class TestClass:
2 def method(self):
3 print("测试方法")
4
5 test = TestClass()
6 print(TestClass.method) #<unbound method TestClass.method>
7 print(test.method) #<bound method TestClass.method of <__main__.TestClass object at 0x021B46D0>>
8
9 TestClass.method(test) #测试方法
10 test.method() #测试方法

1 # 私有成员
2 class TestClass:
3 __private_property = 1
4
5 def __private_method():
6 pass
7
8 print(TestClass.__dict__) # {'__module__': '__main__', '_TestClass__private_method': <function __private_method at 0x0212B970>, '_TestClass__private_property': 1

1 #多重继承
2 class Base1:
3 pass
4
5 class Base2:
6 pass
7
8 class Child(Base2, Base1):
9 pass
10
11 child = Child()
12 print(isinstance(child, Child)) # True
13 print(isinstance(child, Base2)) # True
14 print(isinstance(child, Base1)) # True

1 class TestClass1:
2 def say(self):
3 print("我是鸭子1")
4
5 class TestClass2:
6 def say(self):
7 print("我是鸭子2")
8
9 def duck_say(duck):
10 duck.say()
11
12 duck_say(TestClass1()) # 我是鸭子1
13 duck_say(TestClass2()) # 我是鸭子2

1 # 调用父类
2 class Base:
3 def say(self):
4 print("Base")
5
6 class Child(Base):
7 def say(self):
8 Base.say(self)
9 super(Child, self).say()
10 print("Child")
11
12 child = Child()
13 child.say()

1 from os.path import join
2
3 class FileObject:
4 '''Wrapper for file objects to make sure the file gets closed on deletion.'''
5
6 def __init__(self, filepath='~', filename='sample.txt'):
7 # open a file filename in filepath in read and write mode
8 self.file = open(join(filepath, filename), 'r+')
9
10 def __del__(self):
11 self.file.close()
12 del self.file

1 class Word(str):
2 '''Class for words, defining comparison based on word length.'''
3
4 def __new__(cls, word):
5 # Note that we have to use __new__. This is because str is an immutable
6 # type, so we have to initialize it early (at creation)
7 if ' ' in word:
8 print "Value contains spaces. Truncating to first space."
9 word = word[:word.index(' ')] # Word is now all chars before first space
10 return str.__new__(cls, word)
11
12 def __gt__(self, other):
13 return len(self) > len(other)
14
15 def __lt__(self, other):
16 return len(self) < len(other)
17
18 def __ge__(self, other):
19 return len(self) >= len(other)
20
21 def __le__(self, other):
22 return len(self) <= len(other)
23
24 print(Word("duan") > Word("wei"))

1 class AccessCounter:
2 '''A class that contains a value and implements an access counter.
3 The counter increments each time the value is changed.'''
4
5 def __init__(self, value):
6 super(AccessCounter, self).__setattr__('counter', 0)
7 super(AccessCounter, self).__setattr__('value', value)
8
9 def __setattr__(self, name, value):
10 if name == 'value':
11 super(AccessCounter, self).__setattr__('counter', self.counter + 1)
12 # Make this unconditional.
13 # If you want to prevent other attributes to be set, raise AttributeError(name)
14 super(AccessCounter, self).__setattr__(name, value)
15
16 def __delattr__(self, name):
17 if name == 'value':
18 super(AccessCounter, self).__setattr__('counter', self.counter + 1)
19 super(AccessCounter, self).__delattr__(name)

1 class FunctionalList:
2 '''A class wrapping a list with some extra functional magic, like head,
3 tail, init, last, drop, and take.'''
4
5 def __init__(self, values=None):
6 if values is None:
7 self.values = []
8 else:
9 self.values = values
10
11 def __len__(self):
12 return len(self.values)
13
14 def __getitem__(self, key):
15 # if key is of invalid type or value, the list values will raise the error
16 return self.values[key]
17
18 def __setitem__(self, key, value):
19 self.values[key] = value
20
21 def __delitem__(self, key):
22 del self.values[key]
23
24 def __iter__(self):
25 return iter(self.values)
26
27 def __reversed__(self):
28 return FunctionalList(reversed(self.values))
29
30 def append(self, value):
31 self.values.append(value)
32 def head(self):
33 # get the first element
34 return self.values[0]
35 def tail(self):
36 # get all elements after the first
37 return self.values[1:]
38 def init(self):
39 # get elements up to the last
40 return self.values[:-1]
41 def last(self):
42 # get last element
43 return self.values[-1]
44 def drop(self, n):
45 # get all elements except first n
46 return self.values[n:]
47 def take(self, n):
48 # get first n elements
49 return self.values[:n]

1 class Entity:
2 '''Class to represent an entity. Callable to update the entity's position.'''
3
4 def __init__(self, size, x, y):
5 self.x, self.y = x, y
6 self.size = size
7
8 def __call__(self, x, y):
9 '''Change the position of the entity.'''
10 self.x, self.y = x, y
11 print(x, y)
12
13 entity = Entity(5, 1, 1)
14 entity(2, 2)

1 class Closer:
2 def __enter__(self):
3 return self
4
5 def __exit__(self, exception_type, exception_val, trace):
6 print("清理完成")
7 return True;
8
9 with Closer() as closer:
10 pass

1 class Meter(object):
2 '''Descriptor for a meter.'''
3
4 def __init__(self, value=0.0):
5 self.value = float(value)
6 def __get__(self, instance, owner):
7 return self.value
8 def __set__(self, instance, value):
9 self.value = float(value)
10
11 class Foot(object):
12 '''Descriptor for a foot.'''
13
14 def __get__(self, instance, owner):
15 return instance.meter * 3.2808
16 def __set__(self, instance, value):
17 instance.meter = float(value) / 3.2808
18
19 class Distance(object):
20 '''Class to represent distance holding two descriptors for feet and
21 meters.'''
22 meter = Meter()
23 foot = Foot()

1 # coding=utf-8
2
3 def paly(self):
4 print("游戏中...")

1 # coding=utf-8
2
3 class Animal:
4 from playable import paly
5
6 animal = Animal()
7 animal.paly() # 游戏中...

1 #coding:utf-8
2
3 class TestClass:
4 def method1(self):
5 print("方法1")
6
7 def method2(self):
8 print("方法2")
9
10 TestClass.method2 = method2
11
12 test = TestClass()
13 test.method1() # 方法1
14 test.method2() # 方法2

1 TestClass = type("TestClass", (object,), {
2 "say": lambda self : print("你好啊")
3 })
4
5 test = TestClass()
6 test.say()

1 def getter(name):
2 def getterMethod(self):
3 return self.__getattribute__(name)
4 return getterMethod
5
6 def setter(name):
7 def setterMethod(self, value):
8 self.__setattr__(name, value)
9 return setterMethod
10
11 class TestClass:
12 getName = getter("name")
13 setName = setter("name")
14
15 test = TestClass()
16 test.setName("段光伟")
17 print(test.getName())