python inserting variable string as file name


I'm trying to create a file file a unique file name, every time my script is ran, it's only intended to be weekly or monthly. so I chose to use the date for the file name.

f = open('%s.csv', 'wb') %name

is where I'm getting this error.

Traceback (most recent call last):
File "C:\Users\User\workspace\new3\stjohnsinvoices\", line 143,      in <module>
f = open('%s.csv', 'ab') %name
TypeError: unsupported operand type(s) for %: 'file' and 'str'

it works if I use a static filename, is there an issue with the open function, that means you can't pass a string like this?

name is a string and has values such as :


Many thanks for any help

This question is tagged with python file python-2.7

~ Asked on 2013-01-31 09:25:56

The Best Answer is


You need to put % name straight after the string:

f = open('%s.csv' % name, 'wb')

The reason your code doesn't work is because you are trying to % a file, which isn't string formatting, and is also invalid.

~ Answered on 2013-01-31 09:27:34


you can do something like

filename = "%s.csv" % name
f = open(filename , 'wb')

or f = open('%s.csv' % name, 'wb')

~ Answered on 2013-01-31 09:27:27

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