Python中的map函数有什么用途？

map(function, iterator1,iterator2 ...iteratorN)

# creating a function that accepts the number as an argumentdef exampleMapFunction(num):   # adding 5 to each number in a list and returning it   return num+5 # input listinputList = [3, 5, 1, 6, 10] # Passing above defined exampleMapFunction function# and given list to the map() function# Here it adds 5 to every element of the given list modifiedList = map(exampleMapFunction, inputList)# printing the modifies list(map object)print(modifiedList)# converting the map object to the list and printing it print("Adding 5 to each element in a list using map():", list(modifiedList))

<map object at>Adding 5 to each element in a list using map(): [8, 10, 6, 11, 15]</map>

# creating a function that accepts the number as an argumentdef exampleMapFunction(num):   # adding 5 to each number in a dictionary and returning it   return num + 5 # input DictionaryinputDictionary = {2, 3, 4, 5, 6, 7, 8, 9} # passing above defined exampleMapFunction function# and input dictionary to the map() function# Here it adds 5 to every element of the given dictionary modifiedDict = map(exampleMapFunction, inputDictionary)# printing the modified dictionary(map object)print(modifiedDict)# converting the map object to the list and printing itprint("Adding 5 to each element in a dictionary using map():", list(modifiedDict))

<map object at>Adding 5 to each element in a dictionary using map(): [7, 8, 9, 10, 11, 12, 13, 14]</map>

# creating a function that accepts the number as an argumentdef exampleMapFunction(i):   # converting each item in tuple into lower case   return i.lower() # input tupleinputTuple = ('HELLO', 'TUTORIALSPOINT', 'pyTHON', 'CODES') # passing above defined exampleMapFunction function# and input tuple to the map() function# Here it converts every element of the tuple to lower case modifiedTuple = map(exampleMapFunction, inputTuple)# printing the modified tuple(map object)print(modifiedTuple) print('Converting each item in a tuple to lowercase:')# converting the map object to the list and printing itprint(list(modifiedTuple))

<map object at>Converting each item in a tuple to lowercase:['hello', 'tutorialspoint', 'python', 'codes']</map>

# importing math moduleimport math  # creating a function that returns whether the number # passed is a positive number or not def isPositive(n):    return n >= 0  # creating a function that filters all the positive numbers# from the list and returns the square root of them. def filterSqrtofPositive(nums):    # filtering all the positive numbers from the list using filter()   # and returning the square root of them using the math.sqrt and map()     filteredItems = map(math.sqrt, filter(isPositive, nums))    # returning the list of filetred elements   return list(filteredItems)  # input listinputList= [16, -10, 625, 25, -50, -25]# calling the function by passing the input list print(filterSqrtofPositive(inputList))

[4.0, 25.0, 5.0]