Printing output to file with Python

Question

I am trying to create a script that takes a file as input, looks up all the email addresses, and writes them to a designated file.

based on other similar questions, i have ended up with this:

import re

    Input = open("inputdata.txt", "r")
    regex = re.compile("\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b")
    Logfile = "Result.txt"


        for line in Input:
            query = regex.findall(line)
            for line in query:
                print >>Logfile, query

what am i doing wrong? this outputs nothing. i am guessing the main problem is "for line in query:", which i have tried changing without any luck.

Cheers!

Edit: i have changed the script as suggested below, with "print (query)" instead. i still do not get any output. current script is:

import re

Input = open("Inputdata.txt", "r")
regex = re.compile("\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b")
# logfile = "Result.txt"

for line in Input:
    query = regex.findall(line)
    for line in query:
        with open("Result.txt", "a") as logfile:
            logfile.write(line)

It outputs nothing, and tells me: " NameError: name "logfile" not defined". what causes this, and is this the reason there is no output?

Concerning your edit: I do not get a name error for that code; are you sure you are using this exact code? Note that I changed the variable from Logfile to logfile (i.e. lower case) to comply to coding conventions. Also, you do not have to open the file anew in each iteration. Move the with ... line on top of your loop. — tobias_k
– tobias_k, Commented Mar 25, 2015 at 12:08

tobias_k · Accepted Answer · 2015-03-25 09:54:00Z

1

Your Logfile variable is just the name of a file, not an actual file object. Also, you should use with to automatically close the file when you are done. Try this:

with open("Result.txt", "a") as logfile:
    print >>logfile, "hello world"
    print >>logfile, "another line"

But note that in Python 3.x, the syntax is different, as print is no longer a statement but a function:

with open("Result.txt", "a") as logfile:
    print("hello world", file=logfile)
    print("another line", file=logfile)

Thus, instead of redirecting print, the best choice might be to write to the file directly:

with open("Result.txt", "a") as logfile:
    logfile.write("hello world\n")
    logfile.write("another line\n")

answered Mar 25, 2015 at 9:54

tobias_k

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Krisem Over a year ago

Thanks alot for this. The working script looks like this, and now outputs correctly: import re Input = open("Input.txt", "r") regex = re.compile("\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b") # logfile = open("Result.txt", "a") with open("Result.txt", "a") as logfile: for line in Input: query = regex.findall(line) for query in Input: logfile.write(query)

RatDon · Accepted Answer · 2015-03-25 09:41:16Z

0

I don't think, with print you can write to a file without redirecting the output to a file. The way you have used the print, I guess, you want output redirection only.

Let's say your python script is in a file test.py. replace the line:

print >>Logfile, query

with just:

print query

And from a terminal/cmd, run the script like this:

python test.py >> Result.txt

This is called output redirection.

answered Mar 25, 2015 at 9:41

RatDon

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