1. python-for循环
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循环详解图
for语句:一般用于遍历数据类型的元素进行处理,例如字符串、列表。
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循环语法格式:
for <变量> in <序列>: <代码块>
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示例代码
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示例1:遍历字符串
s = "123456" for i in s: print(i)
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示例2:遍历列表
computer = ["主机","显示器","鼠标","键盘"] for i in computer: print(i,len(i))
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示例3:遍历字典
computer = {"主机":5000,"显示器":1000,"鼠标":60,"键盘":150} for i in computer.items(): print(i) print("名称: %s\t价格: %s" % (i[0],i[1]))
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示例4:嵌套循环
s1 = "123456" s2 = "456789" for i in s1: for x in s2: if i == x: print(i)
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range()内建函数:
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动态生成数字序列,例如range(1,6),结果类似列表[1,2,3,4,5,6]
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示例:生成0-4序列
for i in range(5): print(i)
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2. 案例
2.1、案例1:for循环基础使用
#!/usr/bin/env python3
# _*_ coding: utf-8 _*_
# Author:shichao
# File: .py
for i in range(1,5,1):
print("开始种花第{}次".format(i))
2.2 案例2:示例代码
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示例1:遍历字符串
# 示例代码1:循环字符串 s = "123456" for i in s: print(i)
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示例2:遍历列表
# 示例代码2: 遍历列表 computer = ["主机","显示器","鼠标","键盘"] for i in computer: print(i)
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示例3:遍历字典
# 示例代码3:遍历字典 computer = {"主机":5000,"显示器":1000,"鼠标":60,"键盘":150} for n,i in computer.items(): # computer.item获取所有的键值,n为循环的键,i为循环的值 print("名称: %s\t价格: %s" %(n,i))
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示例4:嵌套循环
# 示例代码4:嵌套循环 s1 = "123456" s2 = "456789" for i in s1: # 循环s1字符串,第一次i,输出1 for x in s2: # 循环s2字符串,第一次i输出后,s2要循环整个过程4-9,依次类推 if i == x: print(i)
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示例5:range内置函数使用
#示例代码5: range循环 for i in range(5): # range循环,最后一个数不会打印 range(1,5,1) range的第一个为开始值,第二个为最终值,后面一位为步长 print(i)