Python中的匿名函数是什么

匿名函数

lambda x , y : x+y

1.匿名的目的就是要没有名字，给匿名函数赋给一个名字是没有意义的。

2.匿名函数的参数规则、作用域关系与有名函数是一样的。

3.匿名函数的函数体通常应该是 一个表达式,该表达式必须要有一个返回值。

f=lambda x,n:x ** n

print(f(2,3))

lambda匿名函数的应用：**max,min,sorted,map,reduce,filter**

求工资最高的人：max

salaries={
'egon':3000,
'alex':100000000,
'wupeiqi':10000,
'yuanhao':2000
}
defget(k):
returnsalaries[k]
print(max(salaries,key=get))#'alex'
print(max(salaries,key=lambdax:salaries[x]))
info=[
{'name':'egon','age':'18','salary':'3000'},
{'name':'wxx','age':'28','salary':'1000'},
{'name':'lxx','age':'38','salary':'2000'}
]
max(info,key=lambdadic:int(dic['salary']))
max([11,22,33,44,55])

求工资最低的人：min

salaries={
'egon':3000,
'alex':100000000,
'wupeiqi':10000,
'yuanhao':2000
}
print(min(salaries,key=lambdax:salaries[x]))#'yuanhao'
info=[
{'name':'egon','age':'18','salary':'3000'},
{'name':'wxx','age':'28','salary':'1000'},
{'name':'lxx','age':'38','salary':'2000'}
]
min(info,key=lambdadic:int(dic['salary']))

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sort把薪资字典，按照薪资的高低排序

salaries={
'egon':3000,
'alex':100000000,
'wupeiqi':10000,
'yuanhao':2000
}
alaries=sorted(salaries)#默认按照字典的键排序
print(salaries)
#salaries=sorted(salaries,key=lambdax:salaries[x])#默认是升序排
alaries=sorted(salaries,key=lambdax:salaries[x],reverse=True)#降序
print(salaries)
info=[
{'name':'egon','age':'18','salary':'3000'},
{'name':'wxx','age':'28','salary':'1000'},
{'name':'lxx','age':'38','salary':'2000'}
]
l=sorted(info,key=lambdadic:int(dic['salary']))

map 映射, 循环让每个元素执行函数，将每个函数执行的结果保存到新的列表中

v1=[11,22,33,44]
result=map(lambdax:x+100,v1)#第一个参数为执行的函数,第二个参数为可迭代元素.
print(list(result))#[111,122,133,144]
names=['alex','wupeiqi','yuanhao','egon']
res=map(lambdax:x+'_NB'ifx=='egon'elsex+'_SB',names)
print(list(res))

reduce , 对参数序列中元素进行累积

importfunctools
v1=['wo','hao','e']
deffunc(x,y):
returnx+y
result=functools.reduce(func,v1)
print(result)#wohaoe
result=functools.reduce(lambdax,y:x+y,v1)
print(result)#wohaoe
fromfunctoolsimportreduce
l=['my','name','is','alex','alex','is','sb']
res=reduce(lambdax,y:x+''+y+'',l)
print(res)
#mynameisalexalexissb

filter , 按条件筛选

result=filter(lambdax:x>2,[1,2,3,4])
print(list(result))
v1=[11,22,33,'asd',44,'xf']
#一般做法
deffunc(x):
iftype(x)==int:
returnTrue
returnFalse
result=filter(func,v1)
print(list(result))#[11,22,33,44]
#简化做法
result=filter(lambdax:Trueiftype(x)==intelseFalse,v1)
print(list(result))
#极简做法
result=filter(lambdax:type(x)==int,v1)
print(list(result))
names=['alex_sb','wxx_sb','yxx_sb','egon']
res=filter(lambdax:Trueifx.endswith('sb')elseFalse,names)
res=filter(lambdax:x.endswith('sb'),names)
print(list(res))#['alex_sb','wxx_sb','yxx_sb']
ages=[18,19,10,23,99,30]
res=filter(lambdan:n>=30,ages)
print(list(res))#[99,30]
salaries={
'egon':3000,
'alex':100000000,
'wupeiqi':10000,
'yuanhao':2000
}
res=filter(lambdak:salaries[k]>=10000,salaries)
print(list(res))#['alex','wupeiqi']