8.13 anonymous function

A named function

Function function name used is based.

def func():
    pass
func()

Anonymous function

Anonymous function, he has no name binding, ie, once recovered, either bracketed run.

print(lambda x,y: x+y)
# <function <lambda> at 0x0000028D950DC158>

res = lambda x,y:x+y
print(res(1,2))
# 3

Built-in function in combination with

Generally anonymous functions max (), sorted (), filter (), sorted () method in combination.

salary_dict = {
    'nick': 3000,
    'jason': 100000,
    'tank': 5000,
    'sean': 2000
}

1. If we want to remove the highest-paid people from the dictionary, we can use the max () method, but the max () the comparison is the default dictionary key.

First iterables become iterator object
res = next (iterator object), the parameters passed to the function key res as specified, and returns the value as determined according to the function

print(max(salary_dict,key=lambda k:salary_dict[k]))  # jason

2. If we want the dictionary in the above-mentioned people descending order according to salary, you can use the sorted () method.

sorted () works:

First iterables become iterator object
res = next (iterator object), res as the argument to the function specified by the first parameter, and returns the value as determined according to the function.

print(sorted(salary_dict,key=lambda k:salary_dict[k])) 
# ['sean', 'nick', 'tank', 'jason']

3. If we want a list of names to do a deal, you can use the map () method.

map () works:

First iterables become iterator object
res = next (iterator object), res as the argument to a function specified by the first parameter, and then returns as one map () method of the function result value.

lis = ['jason', 'tank', 'sean']
res = map(lambda name:f'{name} sb',lis)
print(list(res))
# ['jason sb', 'tank sb', 'sean sb']

4. If we want to filter contains the name of the name 'sb' in addition, we can use the filter () method.

filter () works:

First iterables become iterator object
res = next (iterator object), as a function of the res parameters specified by the first parameter passed, then the filter will determine the return value of the function is true, if true left.

lis = ['jason sb', 'tank sb', 'sean sb','nick']
res1 = filter(lambda i:i.endswith('sb'),lis)
print(list(res1))
# ['jason sb', 'tank sb', 'sean sb']