将不同数量的字符附加到字符串列表中的字符串

Question

Let's say I have a list of strings:

strs = ["aa", "bbb", "c", "dddd"]

I want to append spaces to the end of each string so that each string is 4 characters long. That is, I want the end product to look like this:

strs_final = ["aa  ", "bbb ", "c   ", "dddd"]

I think list comprehension is the way to go, but I'm not sure exactly how to go about doing this. I know how to, for instance, pick out the strings that are of length 3 and add one space to them:

[i+" " for i in strs if len(i) == 3]

But I don't know how to add varying numbers of spaces for varying lengths of strings

Answer 1

另一种解决方案是使用str.ljust

[i.ljust(4) for i in strs]

Answer 2

You can use python's format . The general form for format specifier is:

format_spec ::=  [[fill]align][sign][#][0][width][,][.precision][type]

so, if you provide the width it will be padded with space:

>>> list(map('{:4}'.format, strs))
['aa  ', 'bbb ', 'c   ', 'dddd']

Answer 3

>>> [i+" "*(4-len(i)) for i in strs]
['aa  ', 'bbb ', 'c   ', 'dddd']

The key point being "x"*4 gives you "xxxx"