Question

I am attempting to open and write to a file at the end of some for loop I have. However,
I get a “output” undefined prompt. (See code below)

Am I not declaring what output is as the same time I open my file ‘output.txt’ in write mode?

for X in Y
    ....
    output = open(output.txt, 'w')
    output.writelines(lines)
    output.close()

This should be working right? is my syntax wrong? Or must I declare output = open outside of the for loop?

Notes: Python 2.7.3

Answered: Thank you all, I was trying to open output.txt not ‘output.txt’ hence python couldn’t understand my declaration.

Answer 1

The filename output.txt is a string, but you have not quoted it. So the undefined output Python complains about is not the variable result of the open() call, but rather the improperly quoted string inside the open() call.

It gets misinterpreted as some object called open on which you are accessing a property txt.

output = open('output.txt', 'w')