Fwd: Python new user question - file writeline error

[Jussi Salmela]

Shawn Milo kirjoitti:
> To the list:
> 
> I have come up with something that's working fine. However, I'm fairly
> new to Python, so I'd really appreciate any suggestions on how this
> can be made more Pythonic.
> 
> Thanks,
> Shawn
> 
> 
> 
> 
> 
> 
> Okay, here's what I have come up with:

What follows may feel harsh but you asked for it ;)

> 
> 
> #! /usr/bin/python
> 
> import sys
> import re
> 
> month 
> ={'JAN':1,'FEB':2,'MAR':3,'APR':4,'MAY':5,'JUN':6,'JUL':7,'AUG':8,'SEP':9,'OCT':10,'NOV':11,'DEC':12} 
> 
> infile=file('TVA-0316','r')
> outfile=file('tmp.out','w')
> 
> def formatDatePart(x):
>        "take a number and transform it into a two-character string,
> zero padded"
If a comment or doc string is misleading one would be better off without
it entirely:
	"take a number": the function can in fact take (at least)
	any base type
	"transform it": the function doesn't transform x to anything
			although the name of the variable x is the same
			as the argument x
	"two-character string": to a string of at least 2 chars
	"zero padded": where left/right???
>        x = str(x)
>        while len(x) < 2:
>                x = "0" + x
You don't need loops for these kind of things. One possibility is to 
replace the whole body with:
	return str(x).zfill(2)
>        return x
> 
> regex = re.compile(r",\d{2}/[A-Z]{3}/\d{4},")
> 
> for line in infile:
>        matches = regex.findall(line)
>        for someDate in matches:
> 
Empty lines are supposed to make code more readable. The above empty
line does the contrary by separating the block controlled by the for
and the for statement
>                dayNum = formatDatePart(someDate[1:3])
>                monthNum = formatDatePart(month[someDate[4:7]])
>                yearNum = formatDatePart(someDate[8:12])
You don't need the formatDatePart function at all:
	newDate = ",%4s-%02d-%2s," % \
		(someDate[8:12],month[someDate[4:7]],someDate[1:3])
> 
>                newDate = ",%s-%s-%s," % (yearNum,monthNum,dayNum)
>                line = line.replace(someDate, newDate)
> 
>        outfile.writelines(line)
> 
> infile.close
> outfile.close
You have not read the answers given to the OP, have you. Because if you 
had, your code would be:
	infile.close()
	outfile.close()
The reason your version seems to be working, is that you probably 
execute your code from the command-line and exiting from Python to 
command-line closes the files, even if you don't.

Cheers,
Jussi