deforder_1(): a = int(input("请输入一个在20(包含)到80(不包含)之间的整数:")) # 断言,如果不符合条件则报AssertionError错误 assert80 > a >= 20 if __name__ == '__main__': order_1()
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请输入一个在20(包含)到80(不包含)之间的整数:10 Traceback (most recent call last): File "List_Tuple_Dict.py", line 8, in <module> dict_1() File "List_Tuple_Dict.py", line 4, in dict_1 assert 80 > a >= 20 AssertionError
1.2 循环结构
1.2.1 while循环
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defcycle_1(): a = 10 while a > 0: print(a, end=" ") a -= 1
if __name__ == '__main__': cycle_1()
1
10 9 8 7 6 5 4 3 2 1
1.2.2 for-in循环
遍历列表(元组)
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defcycle_1(): a = list(range(1, 10)) for i in a: print(i, end=" ")
if __name__ == '__main__': cycle_1()
1
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遍历字典
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defcycle_1(): dict_1 = {'语文': 89, '数学': 90, '英语': 100} for key, value in dict_1.items(): print(key, value)
for key in dict_1.keys(): print(key)
for value in dict_1.values(): print(value)
if __name__ == '__main__': cycle_1()
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语文 89 数学 90 英语 100 语文 数学 英语 89 90 100
1.2.3 循环使用else
Python的循环都可以定义else代码块(其他编程语言通常不支持)
为while循环定义else:
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defcycle_1(): a = 10 while a > 0: print(a, end=" ") a -= 1 else: print(-1)
if __name__ == '__main__': cycle_1()
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10 9 8 7 6 5 4 3 2 1 -1
为for循环定义else:
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defcycle_1(): a = list(range(1, 10)) for i in a: print(i, end=" ") else: print(-1)
if __name__ == '__main__': cycle_1()
1
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1.2.4 for表达式
用于利用其他可迭代对象(列表,元组等)创建新的列表.
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defcycle_1(): a = list(range(10)) print(a) # 将a中的所有元素扩大两倍,生成新的列表list_a list_a = [i * 2for i in a] # 可以在后面加上if条件 list_b = [i * 2for i in a if i % 2 != 0] print(list_a) print(list_b)