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ValueError: zero length field name in format - Running under Python 2.7.3?

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  ValueError: zero length field name in format - Running under Python 2.7.3? Victor Hooi <victorhooi@gmail.com> - 2013-11-04 14:33 -0800
    Re: ValueError: zero length field name in format - Running under Python 2.7.3? Chris Angelico <rosuav@gmail.com> - 2013-11-05 10:02 +1100
      Re: ValueError: zero length field name in format - Running under Python 2.7.3? Victor Hooi <victorhooi@gmail.com> - 2013-11-04 15:44 -0800

#58463 — ValueError: zero length field name in format - Running under Python 2.7.3?

Hi,

I have a Python script that's using a format string without positional specifiers. I.e.:

    LOG_FILENAME = 'my_something_{}.log'.format(datetime.now().strftime('%Y-%d-%m_%H.%M.%S'))

I'm running this from within a virtualenv, running under Python 2.7.3.

    $ python -V
    Python 2.7.3
    $ which python
    /opt/my_project_venv/bin/python

The first line of the script is:

    #!/usr/bin/env python

However, when I run this line, I get the following error:

    Traceback (most recent call last):
      File "my_script.py", line 25, in <module>
        LOG_FILENAME = 'my_something_{}.log'.format(datetime.now().strftime('%Y-%d-%m_%H.%M.%S'))
    ValueError: zero length field name in format


The weird thing, when I start a Python REPL and run that line interactively, it works fine:

    $ python
    Python 2.7.3 (default, Jan  7 2013, 11:52:52)
    [GCC 4.4.6 20120305 (Red Hat 4.4.6-4)] on linux2
    Type "help", "copyright", "credits" or "license" for more information.
    >>> from datetime import datetime
    >>> LOG_FILENAME = 'my_project_{}.log'.format(datetime.now().strftime('%Y-%d-%m_%H.%M.%S'))
    >>> print(LOG_FILENAME)
    my_project_2013-05-11_09.29.47.log

My understanding was that in Python 2.7/3.1, you could omit the positional specifiers in a format string.



Cheers,
Victor

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#58466

On Tue, Nov 5, 2013 at 9:33 AM, Victor Hooi <victorhooi@gmail.com> wrote:
> However, when I run this line, I get the following error:
>
>     Traceback (most recent call last):
>       File "my_script.py", line 25, in <module>
>         LOG_FILENAME = 'my_something_{}.log'.format(datetime.now().strftime('%Y-%d-%m_%H.%M.%S'))
>     ValueError: zero length field name in format
>
>
> The weird thing, when I start a Python REPL and run that line interactively, it works fine

Google tells me that that was an issue in Python 2.6, so my first
check would be to see what `/usr/bin/env python` actually gives you -
are you running inside an environment that changes your path? Drop a
"import sys; print(sys.version)" at the top of your script and see
what it's really running as.

ChrisA

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#58468

Hi,

You're right - it was sudo playing up with the virtualenv.

The script was in /opt, so I was testing with sudo to get it to run.

I should have setup a service account, and tested it with that =).

$ python sync_bexdb.py
2.7.3 (default, Jan  7 2013, 11:52:52)
[GCC 4.4.6 20120305 (Red Hat 4.4.6-4)]

$ sudo python sync_bexdb.py
[sudo] password for victor:
2.6.6 (r266:84292, Jul 10 2013, 22:48:45)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)]

Cheers,
Victor

On Tuesday, 5 November 2013 10:02:50 UTC+11, Chris Angelico  wrote:
> On Tue, Nov 5, 2013 at 9:33 AM, Victor Hooi <victorhooi@gmail.com> wrote:
> 
> > However, when I run this line, I get the following error:
> 
> >
> 
> >     Traceback (most recent call last):
> 
> >       File "my_script.py", line 25, in <module>
> 
> >         LOG_FILENAME = 'my_something_{}.log'.format(datetime.now().strftime('%Y-%d-%m_%H.%M.%S'))
> 
> >     ValueError: zero length field name in format
> 
> >
> 
> >
> 
> > The weird thing, when I start a Python REPL and run that line interactively, it works fine
> 
> 
> 
> Google tells me that that was an issue in Python 2.6, so my first
> 
> check would be to see what `/usr/bin/env python` actually gives you -
> 
> are you running inside an environment that changes your path? Drop a
> 
> "import sys; print(sys.version)" at the top of your script and see
> 
> what it's really running as.
> 
> 
> 
> ChrisA

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