Python编程：日常练习-1

1.运算符的优先级

print(3*1**3) #3 相当于：3*(1**3)

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2.小整数池

a = 1 b = 1 print(a is b) # True a = 300 b = 300 print(a is b) # True # 在shell里是False # [-5, 256]之间的整数，值相同的整数共享一个对象 # is 比较内存地址 # == 比较对象的值

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3.字符串

def foo1(a): a = a +"2" a = a * 2 return a print(foo1("hello")) # hello2hello2 # 操作符重载 # __add__(+) # __mul__(*) #例如： class Point(object): def __init__(self, x, y): self.x = x self.y = y def __add__(self, other): return Point(self.x + other.x, self.y + other.y) def __mul__(self, other): return Point(self.x * other.x, self.y * other.y) def __repr__(self): return "Point({}, {})".format(self.x, self.y) p1=Point(1,2) p2=Point(3,4) print(p1+p2) # Point(4, 6) print(p1*p2) # Point(3, 8)

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4.浮点数

print(0.3) # 0.3 print(0.1 + 0.2) # 0.30000000000000004 print(0.1 + 0.2 == 0.3) # False

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5.取反操作

print(~5) # -6 print(~~5) # 5 print(~~~5) # -6 # ~按位取反，计算机以补码存储

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6.布尔

print(bool("Flase")) # True

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7.链式比较

print(True == False ) # False print(False ==False) # True print(True == False ==False) # False # 相当于 (True == False) and (False == False)

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8.循环语句

i = 0 while i < 5: print(i) i += 1 if i ==3: break else: print(0) """ 0 1 2 """

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9.作用域

x = 12 def f1(): x = 3 print(x) def f2(): global x # 没有这个声明报错，local variable 'x' referenced before assignment x += 1 print(x) f1() f2()

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10.python关键字

eval("1-1") # eval不是关键字，是内建函数 assert(1 == 1) pass # nonlocal import keyword print(keyword.kwlist) """33 ['False', 'None', 'True', 'and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield'] """

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习题来源：《Python知识冲顶大会》

http://mp.weixin.qq.com/s/4FfwEdPYhPoCAlKiz2Hk8w

习题解答：《这10个题，有 68% 的人答不对》

http://mp.weixin.qq.com/s/9PFo10K5xXYUZlL9x8QjBA

Python

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