cannot write to file after close()

[Rainer Hubovsky]

Hello Python-Gurus,

==========================
f = open(LOGFILE,'w')
f.write(time + '\n')
f.close

command = 'ping -n 20' + target + '>>' + LOGFILE
system(command)
==========================

produces an error saying that a file cannot be accessed because it is used
by another process. I asume it is f which is used but don't understand why.

Any ideas?

Thanks a lot!

Cheers,
Rainer

 

[Reinhold Birkenfeld]

Hello Python-Gurus,

==========================
f = open(LOGFILE,'w')
f.write(time + '\n')
f.close

command = 'ping -n 20' + target + '>>' + LOGFILE
system(command)
==========================

produces an error saying that a file cannot be accessed because it is used
by another process. I asume it is f which is used but don't understand why.

Any ideas?

Is the above exactly your code? If yes, it should be

f.close()

The parentheses are necessary to make the statement a function call.

Reinhold

 

[Rainer Hubovsky]

Thank you Reinhold, that was the solution. But just because I am curious:
what is this statement without the parentheses? After all it is a valid
statement...

Rainer

 

[Fredrik Lundh]

Thank you Reinhold, that was the solution. But just because I am curious:
what is this statement without the parentheses? After all it is a valid
statement...

it's an expression that fetches the "close" method object, and throws
it away. to see what it evaluates to, try running the code from the
interactive prompt (or add a print statement):
<built-in method close of file object at 0x00836B20>

also see

http://docs.python.org/ref/exprstmts.html
http://docs.python.org/ref/attribute-references.html

</F>

 

[Reinhold Birkenfeld]

Thank you Reinhold, that was the solution. But just because I am curious:
what is this statement without the parentheses? After all it is a valid
statement...

Rainer

In addition to what Fredrik said, this can be useful for shortcutting a name,
such as

c = f.close
c()

Reinhold