[newbie] file object not returned by function?

[Alex Martelli]

Eur van Andel wrote:

> Hi
> 
> I tried this:
> 
>>from time import strftime, localtime
>>
>>
>>def make_logfile():
>>    logfile = open(strftime("%d-%m-%Y_%H-%M.log", localtime()),'w')
>>    logfile.write('temperatures and pump duty cycles\n')
>>    logfile.write('from six fans and pump controller\n')
>>    return(logfile)
>>
>>
>>logfile = make_logfile

Note that you're NOT calling the function, just assigning it to
the name logfile.  Put parentheses after the functionname to call it.

>>T1 = 20
>>T2 = 30
>>T3 = 40
>>
>>logfile.write("T1, T2, T3")  # I know this does not work :-)
> 
> Traceback (most recent call last):
>   File "file_try.py", line 19, in ?
>     logfile.write("T1, T2, T3")
> AttributeError: 'str' object has no attribute 'write'

This is absolutely unexplicable: logfile cannot be a str, it's
a function-object.  Have you copy-and-pasted everything?!

 
> Why can't a function return a file object?

Sure it can!  Only if you call it, though -- if you don't call
the function it can't return anything.


Alex