Question

What is the use of ‘\’ tags in python string. For example, I have to execute this command:

cmd = 'exec ' + cs_bin + ' ' +  \
               vmtree.rsplit('-', 1)[1].split('/')[0] + ' --xml ' \
               + tmp_corefile + ' | ' + XML2HTML 

what are ‘\’ used for?
Thank you.

Answer 1

\ is used for line continuation.

However you should only use it when required:

Quoted from PEP-8:

The preferred way of wrapping long lines is by using Python’s implied line continuation inside parentheses, brackets and braces. Long lines can be broken over multiple lines by wrapping expressions in parentheses. These should be used in preference to using a backslash for line continuation. Make sure to indent the continued line appropriately. The preferred place to break around a binary operator is after the operator, not before it.

IMO this looks better:

cmd = ('exec ' + cs_bin + ' ' +
       vmtree.rsplit('-', 1)[1].split('/')[0] + ' --xml ' + tmp_corefile + ' | ' 
       + XML2HTML)

The reason why the lines are continued instead of having one huge line is also mentioned in PEP-8:

Limit all lines to a maximum of 79 characters.

There are still many devices around that are limited to 80 character lines; plus, limiting windows to 80 characters makes it possible to have several windows side-by-side. The default wrapping on such devices disrupts the visual structure of the code, making it more difficult to understand. Therefore, please limit all lines to a maximum of 79 characters. For flowing long blocks of text (docstrings or comments), limiting the length to 72 characters is recommended.