Defining a list in Python using the multiply opera

问题:

Recently in Python I have encountered this statement:

board.append([' '] * 8)

I have tried to search the Internet with Google to find some more information about this type of statement, but I can't.

I know what the statement does, but I do not understand how, in what manner is doing, that.

This is the first time I have seen the * operator used on a list. Can you please refer me to a place where I can find some more information about this type of statements?

回答1:

Can you please refer me to a place where I can find some more information about this type of statements.

Most of the relevant operators and methods are defined here: Sequence Types.

Specifically s * n is defined as

s * n, n * s -- n shallow copies of s concatenated

Here, s is a sequence and n is a number.

Thus, [' '] * 8 returns a list consisting of eight ' '.

board.append() appends the result to board, which presumably is a list (of lists).

回答2:

It works like this:

>>> L = [0]*10
>>> L
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
>>> 

If you need to know how something works in Python, look it up in the Python documentation, or just experiment with it yourself.