获取多个用户输入的列表和地图之间的区别

Question

从用户获取多个输入的list(int(input()).split())和map(int,input().split())之间有什么区别？

Answer 1

Let's examine them closely:

list(int(input()).split()) expands into

list(           # Make a list out of...
    int(        # the value of... 
        input() # input from the user,
    )           # converted to an integer.
    .split()    # Then, split that.
)

This doesn't make sense. Say you input something like 15 . The input() function returns the string '15' , which gets converted into the integer 15 . Integers don't have a .split() operation, so you get a SyntaxError .

Now, let's look at map(int,input().split()) :

map(             # Apply the function...
    int          # (that is, `int()`)
    ,            # ...to every element in the iterable...
    input()      # (First, take the input from the user,
        .split() # and then split it)
)                # ...and return all that as a list

This time, we input something like 1 5 6 11 13 .

1. The input() function returns the string '1 5 6 11 13' .
2. Then, we call the .split() function on that string, which returns a list of substrings that were separated by whitespace - that is, it returns the list ['1', '5', '6', '11', '13'] . These are still strings, though, and we want integers.
3. Finally, we apply int() to every element of that list, which gets us the end result [1, 5, 6, 11, 13] , except it's in a map data structure (which is more efficient for python to create in this case than a full list)
4. If we want, we could cast that to a list to use it easily - that would just be enclosing that entire expression in list(...) .