How do I check to see if user added '.txt' to file name and add it if they did not?

Question

I'm having an issue that is probably more easy than I am making it out to be. (I am in an intro level programming class)

Basically I am writing a program where I ask a user for a file name, I read info from the file before sorting it in a list and writing it somewhere else. The assignment wants us to ask user for the file name to read from. If the user enters the file name with the '.txt', we carry on with the processing. If they do not, we must add the '.txt' before continuing on. I know how to add the '.txt' to the file name if they did not include it, but I can not figure out how to check first to see if they did.

How do I go about first checking to see if the user wrote the file name with the extension?

I am assuming it has something to do with an if/else statement but I have been baffled.

Thank you

anon582847382 · Accepted Answer · 2014-04-23T15:13:35.617

2

To check + add the extension:

import os.path

if os.path.splitext(filename)[1] != '.txt':  # Ending is not '.txt'.
   filename += '.txt'

Using os.path.splitext to split the base-name and the extension.

edited Apr 23 '14 at 15:13

answered Apr 23 '14 at 15:07

anon582847382

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It is interesting I didn't know this I might use `txtfile = fname.rsplit('.', 1)[0] + '.txt'` – Grijesh Chauhan Apr 23 '14 at 15:11
Easy enough, Thank you – TX_RocketMan Apr 23 '14 at 15:12
@TX_RocketMan If my answer was helpful to you, would you mind accepting it after the grace period has passed? You can do it by clicking the tick below the vote counts so it stays green. Thank you. – anon582847382 Apr 23 '14 at 15:13
This is better than `string.split()`, `string.rsplit()` etc - see a [discussion of this](http://stackoverflow.com/questions/542596) – msnider Apr 23 '14 at 15:14

score 0 · Answer 2 · answered Apr 23 '14 at 15:10

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You can use the endswith (without any additional imports):

fileName += ".txt" if not fileName.endswith('.txt') else ""

If you want to correct the extension you might want to look at os.splitpath

answered Apr 23 '14 at 15:10

Tejas Pendse

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score 0 · Answer 3 · answered Apr 23 '14 at 15:12

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You probably have the filename stored in a str object (ie, a string). Python documents all the operations you can perform on a str object. One of those operations is endswith - this will tell you whether the string object ends with a particular substring.

So if you have the filename stored in a variable called my_filename, you could do the following:

has_extension = my_filename.endswith('.txt')

has_extension will be true if my_filename ends with '.txt', and false otherwise.

Python's odcumentation is fantastic, I would keep a bookmark to it for reference for situations like this

answered Apr 23 '14 at 15:12

Elliott

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Oh nice, this is pretty simple – TX_RocketMan Apr 23 '14 at 15:14
@TX_RocketMan Hard-coding it like that is usually considered bad practice. – anon582847382 Apr 23 '14 at 15:16

How do I check to see if user added '.txt' to file name and add it if they did not?

3 Answers3