如何在python中删除字符串前后的字符？

Question

How do I remove the whitespace and strip of the newline carriage return from a string? I tried:

a = []
for i in range(len(lines)):
     a.append(lines[i].rstrip().lstrip('\n'))

lines is a list of lines that was created with the readlines() function.

Answer 1

str.strip() removes all whitespace from either side of a string, so the easiest way to do what you want is simply:

with open("source.txt") as file:
    a = [line.strip() for line in file]

The problem with your code is you are using str.lstrip() and str.rstrip() the wrong way around - the newline is on the right, but you are trying to strip it from the left. The newline gets stripped as the str.rstrip() strips all whitespace from the right (including newlines), while the str.lstrip("\\n") finds no newline character from the left and so does nothing, hence your problem.

If you need to leave trailing whitespace except the newline, then you would want line.rstrip("\\n").lstrip() - swapping the arguments for the left and right strips from your original code. This would ensure no whitespace other than the newline is stripped, as it would be with the above code.

Note that I use a list comprehension to do this - it's both more readable and efficient, and a good way to do tasks like this.

I also loop directly over the file object, as that is more efficient (the lines do not have to be loaded into memory). Note my use of the the with statement to open files - this is a best practice in Python as it protects you from subtle bugs, and is (again) more readable

Answer 2

a = [line.strip() for line in lines]

我认为最好在将其放入行列表之前进行剥离