CODEWITHSUNDEEP
pythonpython-3.x
Eypros
Eypros

Reputation: 5723

Meaning of {0!s} as formatting parameter

I am quite familiar with python3 formatting options but I haven't faced a {0!s} option before.
In particular the format I encountered was something like:

'{0!s}.xml'.format('VID/' + file)

which as far as I get it it's just a way to render the output of str(arg) and in my case str('VID/') according to this explanation.

So the output would be something like: VID/000.xml for example.

Since my argument is already a str in this case I did not see any difference when I just omit the whole formatting parameter (use {} instead of {0!s}).

Other experiments I made was omitting the leading 0 which produces the same result, while replacing it with another number like 1 produces an error:

IndexError: tuple index out of range

Can someone explain what's the case with this formatting parameter? When should I use it etc?

Upvotes: 0

Views: 177

Answers (1)

rdas
rdas

Reputation: 21285

It's value conversion: https://pyformat.info/#conversion_flags 

{0!s}.xml

Means "For the 0th argument, get the string to to put in the formatted string by calling the __str__ method"

You can also use {0!r} to call the __repr__ method instead

Upvotes: 1

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