python笔记：1.3.5推导式

# -*- coding: utf-8 -*-
"""
Created on Tue May  7 15:27:10 2019

@author: Administrator
"""

# 列表推导式
s1 = ['china', 'uk', 'american', 'japan', 'usa']
u_string = [x.upper() for x in s1 if len(x) > 2]
print(u_string)

#集合推导式
u_string2 = {x.upper() for x in s1 if len(x) > 2}
print(u_string2)

# 字典推导式
mapping = {val:index for index, val in enumerate(s1)}
print(mapping)

运行：

['CHINA', 'AMERICAN', 'JAPAN', 'USA']
{'CHINA', 'USA', 'AMERICAN', 'JAPAN'}
{'china': 0, 'uk': 1, 'american': 2, 'japan': 3, 'usa': 4}