Python 生成式
# 1、列表生成式 l = ['alex_dsb', 'lxx_dsb', 'wxx_dsb', "xxq_dsb", 'egon'] # new_l=[] # for name in l: # if name.endswith('dsb'): # new_l.append(name) # new_l=[name for name in l if name.endswith('dsb')] # new_l=[name for name in l] # print(new_l) # 把所有小写字母全变成大写 # new_l=[name.upper() for name in l] # print(new_l) # 把所有的名字去掉后缀_dsb # new_l=[name.replace('_dsb','') for name in l] # print(new_l) # 2、字典生成式 # keys=['name','age','gender'] # dic={key:None for key in keys} # print(dic) # items=[('name','egon'),('age',18),('gender','male')] # res={k:v for k,v in items if k != 'gender'} # print(res) # 3、集合生成式 # keys=['name','age','gender'] # set1={key for key in keys} # print(set1,type(set1)) # 4、生成器表达式 # g=(i for i in range(10) if i > 3) # !!!!!!!!!!!强调!!!!!!!!!!!!!!! # 此刻g内部一个值也没有 # print(g,type(g)) # print(g) # print(next(g)) # print(next(g)) # print(next(g)) # print(next(g)) # print(next(g)) # print(next(g)) # print(next(g)) with open('笔记.txt', mode='rt', encoding='utf-8') as f: # 方式一: # res=0 # for line in f: # res+=len(line) # print(res) # 方式二: # res=sum([len(line) for line in f]) # print(res) # 方式三 :效率最高 # res = sum((len(line) for line in f)) # 上述可以简写为如下形式 res = sum(len(line) for line in f) print(res)