Joining multiple strings if they are not empty in Python
Question:
I have four strings and any of them can be empty. I need to join them into one string with spaces between them. If I use:
new_string = string1 + ' ' + string2 + ' ' + string3 + ' ' + string4
The result is a blank space on the beginning of the new string if string1 is empty. Also, I have three blank spaces if string2 and string3 are empty.
How can I easily join them without blank spaces when I don’t need them?
Answers:
>>> strings = ['foo','','bar','moo']
>>> ' '.join(filter(None, strings))
'foo bar moo'
By using None in the filter() call, it removes all falsy elements.
strings = ['foo','','bar','moo']
' '.join([x for x in strings if x is not ''])
'foo bar moo'
If you KNOW that the strings have no leading/trailing whitespace:
>>> strings = ['foo','','bar','moo']
>>> ' '.join(x for x in strings if x)
'foo bar moo'
otherwise:
>>> strings = ['foo ','',' bar', ' ', 'moo']
>>> ' '.join(x.strip() for x in strings if x.strip())
'foo bar moo'
and if any of the strings have non-leading/trailing whitespace, you may need to work harder still. Please clarify what it is that you actually have.
I have four strings and any of them can be empty. I need to join them into one string with spaces between them. If I use:
new_string = string1 + ' ' + string2 + ' ' + string3 + ' ' + string4
The result is a blank space on the beginning of the new string if string1 is empty. Also, I have three blank spaces if string2 and string3 are empty.
How can I easily join them without blank spaces when I don’t need them?
>>> strings = ['foo','','bar','moo']
>>> ' '.join(filter(None, strings))
'foo bar moo'
By using None in the filter() call, it removes all falsy elements.
strings = ['foo','','bar','moo']
' '.join([x for x in strings if x is not ''])
'foo bar moo'
If you KNOW that the strings have no leading/trailing whitespace:
>>> strings = ['foo','','bar','moo']
>>> ' '.join(x for x in strings if x)
'foo bar moo'
otherwise:
>>> strings = ['foo ','',' bar', ' ', 'moo']
>>> ' '.join(x.strip() for x in strings if x.strip())
'foo bar moo'
and if any of the strings have non-leading/trailing whitespace, you may need to work harder still. Please clarify what it is that you actually have.