I have a file I'm parsing, on each line in the same column are one of the values; 0, 1 or -1. I want to parse this so that the numeric values are all in line as below. I am trying to this via an if statement with and/or operators. I cannot get my head around the and/or as when I test this with a print statement, output either prints 1's or prints 0's.
Desired output: 0 1 -1 if number.startswith('1' and '0'): return number.append(' ') print number '1' and '0' resolves to just '0':
>>> '1' and '0' '0' Boolean operators are not the same thing English grammatical constructs!
The str.startswith() method takes a tuple of values to test for:
number.startswith(('1', '0')) and it'll return True if your string starts with '1' or it starts with '0'.
However, in this case you can just use string formatting to pad out your number:
return format(int(number), '-2d') This pads your number out to a field two characters wide, leaving space for a negative sign:\
>>> format(-1, '-2d') '-1' >>> format(0, '-2d') ' 0' >>> format(1, '-2d') ' 1' 
The problem is that the expression '1' and '0' is being evaluated as a bool, and will evaluate to '0'. The whole expression will then be if number.startswith('0'): so the '1' is never being checked.
You should to change this
if number.startswith('1' and '0'): To
if number.startswith('1') or number.startswith('0'): Or
if number[0] in ('1', '0'): Firstly, you're using .startswith with a coherent intention, but the arguments don't work that way, try this:
if number.startswith('1', '0'): Secondly, .append does not do what you want. If you want to add a space in front of number if it begins with '1' or '0', try this:
if number.startswith('1', '0'): number = ' ' + number print number Additionally, .append is used to add an item to the end of a list, for example:
>>> list = [1, 2] >>> list.append('x') >>> list [1, 2, 'x'] 