Question

This is a continuation from a question that I had yesterday. I am trying to open a text file that contains a list of numbers. I want to write these numbers to a new file multiple times. The purpose of the loop is to be able to write the source list multiple times. In this example, I want to print a list of 100 numbers 10 times so I end up with a list of 1000 numbers in my output file. This is the code that I am working with:

i = 10
while i > 0:
    with open ('C:/TestReq_100 Records.txt', 'r') as ipf:
       for line in ipf:
            num = line.strip()
            filename = 'processed.txt'
            with open('processed.txt', 'w') as opf:
                opf('%s' %num)


##           print num
    i = i - 1

If I comment out the code related to writing to file and use the print command in the interpreter, the code does what I want. I just can’t seem to get the same output in a text file. Again, I am not a student. Just trying to create files for use in my Company’s software for testing purposes…thanks!

Answer 1

In addition to Levon’s answer, there are a few issues with your current program.

• Rather than manually initializing and decrementing an index, try using xrange to accomplish the same task in a more concise way.

• You’re overwriting processed.txt for each number; you should open it at the same time as the input file.

• What is the purpose of i? As it stands, your program is going to do the exact same thing 10 times because i is never used inside the loop.

• '%s' % num does nothing special when num is already a string.

That said, here’s a cleaner version of your program, although i still does nothing in particular:

for i in xrange(10, 0, -1):
    with open('C:/TestReq_100 Records.txt', 'r') as ipf:
        with open('processed.txt', 'w') as opf:
            for line in ipf:
                num = line.strip()
                opf.write(num)

You may want to clarify the intended output of this program for a better answer.

EDIT: Here is a more efficient solution for copying a file into a new file multiple times:

# Read the input data once.
with open('C:/TestReq_100 Records.txt', 'r') as ipf:
    ipdata = ipf.read()
# Add a newline to the end of the file if there isn't already one present.
# Without this, the last and first lines of the input might become single lines.
if ipdata[-1] != '\n':
    ipdata += '\n'
# Write to the output file multiple times.
with open('processed.txt', 'w') as opf:
    for i in xrange(10):
        opf.write(ipdata)