built-in function,is python already prepar for us ,anytime we can call built-in function when we needed it .
all() dict() help()
all([1,2,'')
eval('1+2+3')
filter(function,sequence)
filter object filter iterator
map(function,sequence)
map object map iterator
map
can realize iterator function
for example:
str=['a','b','c','d']
def fun(str):
if str !='a':
return str
ret =filter(fun,str)
print(list(ret))
str =['a','b','c','d']
def fun2 (str):
return str+'good'
ret = map(fun2,str)
print(ret)
reduce:
from fuctools import reduce
def add(x+y):
return x+y
print(reduce(add,range(1,10))
1+2+3+4+5+6+7+8+9=45
the result of reduce is a value ,object not
lambda:
add=lambda a,b:a+b
conbine reduce and lambda realize factorial effect:
from fuctools import reduce
reduce(lambda a,b:a+b,range(1,101)) 5050
reduce(lambda a,b:a*b,range(1,10))