The map() function is used to apply the function to all items of an iterable collection like list, tuple etc and it returns the list of the result after performing the functionality defined in the applied function.

map()函数用于将函数应用于可迭代集合的所有项目，如list，tuple等，并在执行所应用函数中定义的功能后返回结果列表。

Example:

例：

Given a list of temperatures and we have to convert 1) all the values in Celsius and 2) all the values in Fahrenheit - using map() with lambda.

给定温度列表，我们必须转换1)摄氏温度的所有值和2)华氏度的所有值-使用带有lambda的map()。

1) Approach 1: Using normal way

1)方法1：使用常规方法

# function definition to convert temp. from c to f
def ctof(c):
f=9/5*c+32
return f
# function definition to convert temp. from f to c
def ftoc(f):
c=5/9*(f-32)
return c
# list of the values
temp=[12,45,6,78,5,26,67]
print("Orignal Data   : ",temp)
# list declration to store temp. in C
cel=[]
for t in temp:
x=ftoc(t)
cel.append(x)
print("Celcuis Data   : ",cel)
# list declration to store temp. in F
far=[]
for t in temp:
x=ctof(t)
far.append(x)
print("Farenhiet Data : ",far)

Output

输出量

Orignal Data   :  [12, 45, 6, 78, 5, 26, 67]
Celcuis Data   :  [-11.11111111111111, 7.222222222222222, -14.444444444444445,
25.555555555555557, -15.0, -3.3333333333333335, 19.444444444444446]
Farenhiet Data :  [53.6, 113.0, 42.8, 172.4, 41.0,
78.80000000000001, 152.60000000000002]

2) Approach 2: Using map() with lambda

2)方法2：将map()与lambda结合使用

# list of the values
temp=[12,45,6,78,5,26,67]
print("Orignal Data   : ",temp)
# converting values to cel using map and lambda
cel=list(map(lambda f:5/9*(f-32),temp))
print("Celcuis Data   : ",cel)
# converting values to far using map and lambda
far=list(map(lambda c:9/5*c+32,temp))
print("Farenhiet Data : ",far)

Output

输出量

Orignal Data   :  [12, 45, 6, 78, 5, 26, 67]
Celcuis Data   :  [-11.11111111111111, 7.222222222222222, -14.444444444444445,
25.555555555555557, -15.0, -3.3333333333333335, 19.444444444444446]
Farenhiet Data :  [53.6, 113.0, 42.8, 172.4, 41.0,
78.80000000000001, 152.60000000000002]

翻译自: https://www.includehelp.com/python/lambda-and-map-with-example.aspx