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
}
def get(k):return salaries[k]
print(max(salaries,key=get)) #'alex'
print(max(salaries,key=lambda x:salaries[x]))
info = [{'name': 'egon', 'age': '18', 'salary': '3000'},{'name': 'wxx', 'age': '28', 'salary': '1000'},{'name': 'lxx', 'age': '38', 'salary': '2000'}
]
max(info, key=lambda dic: 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=lambda x: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=lambda dic: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=lambda x:salaries[x]) #默认是升序排
alaries=sorted(salaries,key=lambda x: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=lambda dic: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(lambda x: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(lambda x:x+'_NB' if x == 'egon' else x + '_SB',names) print(list(res))
reduce , 对参数序列中元素进行累积
import functools v1 = ['wo','hao','e'] def func(x,y):return x+y result = functools.reduce(func,v1) print(result) # wohaoe result = functools.reduce(lambda x,y:x+y,v1) print(result) # wohaoe from functools import reduce l=['my','name','is','alex','alex','is','sb'] res=reduce(lambda x,y:x+' '+y+' ',l) print(res) #my name is alex alex is sb
filter , 按条件筛选
result=filter(lambda x:x > 2,[1,2,3,4])
print(list(result))
v1 = [11,22,33,'asd',44,'xf']
# 一般做法
def func(x):if type(x) == int:return Truereturn False
result = filter(func,v1)
print(list(result)) # [11,22,33,44]
# 简化做法
result = filter(lambda x: True if type(x) == int else False ,v1)
print(list(result))
# 极简做法
result = filter(lambda x: type(x) == int ,v1)
print(list(result))
names=['alex_sb','wxx_sb','yxx_sb','egon']
res=filter(lambda x:True if x.endswith('sb') else False,names)
res=filter(lambda x:x.endswith('sb'),names)
print(list(res)) #['alex_sb', 'wxx_sb', 'yxx_sb']
ages=[18,19,10,23,99,30]
res=filter(lambda n:n >= 30,ages)
print(list(res)) #[99, 30]
salaries={'egon':3000,'alex':100000000,'wupeiqi':10000,'yuanhao':2000
}
res=filter(lambda k:salaries[k] >= 10000,salaries)
print(list(res)) #['alex', 'wupeiqi']
