关于生成器的一些杂项
三元表达式
def max2(x,y):
if x > y:
return x
else:
return y
x=10
y=20
res=x if x > y else y
print(res) #20
列表生成式
l=[item**2 for item in range(1,11)]
print(l) #[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
将三个字符串加上'SB'
1) names=['alex','wxx','lxx']
l=[]
for name in names:
l.append(name + 'SB')
names=l
print(names) #['alexSB', 'wxxSB', 'lxxSB']
names=[name+'SB' for name in names]
print(names)
2) # names=['alex','wxx','egon','lxx','zhangmingyan']
l=[]
for name in names:
if name != 'egon':
l.append(name + 'SB')
names=l
names=[name+'SB' for name in names if name != 'egon']
print(names) #['alexSBSB', 'wxxSBSB', 'lxxSBSB', 'zhangmingyanSBSB']
l=[item**2 for item in range(1,5) if item > 2]
print(l) #[9, 16]
将所有字母大写
names=['egon','alex_sb','wupeiqi','yuanhao']
names=[name.upper() for name in names]
print(names) #['EGON', 'ALEX_SB', 'WUPEIQI', 'YUANHAO']
筛选没有'sb'字符的字符串
names=['egon','alex_sb','wupeiqi','yuanhao']
nums=[len(name) for name in names if not name.endswith('sb')]
print(nums) #[4, 7, 7]
字典生成式
s1='hello'
l1=[1,2,3,4,5]
res=zip(s1,l1) # zip('拉链',一个一个对应)
print(res) #<zip object at 0x0000018F01A9CE88> 返回zip(s1,l1)的内存地址
keys=['name','age','sex']
values=['egon',18,'male']
res=zip(keys,values) #zip为:('name', 'egon'), ('age', 18), ('sex', 'male')
print(list(res))#[('name', 'egon'), ('age', 18), ('sex', 'male')]
print(list(res))#[] 值已经全部取出,无值可取
d={}
for k,v in zip(keys,values):#将keys和values解压
d[k]=v # 将解压的key和value添加到字典中
print(d) #{'name': 'egon', 'age': 18, 'sex': 'male'}
2)用字典表达式造字典
keys=['name','age','sex']
values=['egon',18,'male']
d={k:v for k,v in zip(keys,values)}
print(d) #{'name': 'egon', 'age': 18, 'sex': 'male'}
info={'name': 'egon', 'age': 18, 'sex': 'male'}
keys=info.keys()
print(keys) #dict_keys(['name', 'age', 'sex'])
iter_keys=keys.__iter__()
values=info.values()
print(values) #dict_values(['egon', 18, 'male'])
d={k:v for k,v in zip(keys,values)}
print(d) #{'name': 'egon', 'age': 18, 'sex': 'male'}
s={i for i in range(10)}
print(s,type(s)) #{0, 1, 2, 3, 4, 5, 6, 7, 8, 9} <class 'set'>
生成器表达式
g=(i for i in range(10))
print(g) #<generator object <genexpr> at 0x0000014AEA904AF0>
print(next(g)) # 0
print(next(g)) # 1
求最大值
nums=[11,22,33,44,55]
print(max(nums)) #55
打开一个文件求取长度最长行的长度
with open('a.txt',encoding='utf-8') as f:
nums=(len(line) for line in f)
print(max(nums))
print(max(nums))
print(max(nums))
l=['egg%s' %i for i in range(5)]
print(l) #['egg0', 'egg1', 'egg2', 'egg3', 'egg4']
print(next(l)) #TypeError: 'list' object is not an iterator
g=('egg%s' %i for i in range(10)) #生成器表达式
print(g) #<generator object <genexpr> at 0x000001FC45A64AF0>
print(next(g)) #egg0
print(next(g)) #egg1