Match string in python regardless of upper and lower case differences

Question

I'm trying to find a match value from a keyword using python. My values are stored in a list (my_list) and in the below example I'm trying to find the word 'Webcam'. I only want to return the word if it is fully matched.

Using item.find works but only if the case matches (i.e. upper and lower case must be correct). But I want to return the item regardless of the case, However, I do not wish to match all instances of the string like 'Webcamnew' so using the any() method won't work I think. Does anyone know how to do this..?

my_list = ['webcam', 'home', 'Space', 'Maybe later', 'Webcamnew']

for item in my_list:
    if item.find("Webcam") != -1:
        print item

Convert every string you are comparing to lowercase with `string.lower()` — wils484, Jun 19 '14 at 18:05
if there is a way to do it without converting to lower/uppercase that would be useful. — DavidJB, Jun 19 '14 at 18:07

Andrew_CS · Answer 1 · 2014-06-19T18:17:01.730

8

my_list = ['webcam', 'home', 'Space', 'Maybe later', 'Webcamnew']

for item in my_list:
    if 'webcam' == item.lower()
        print item.lower()

Note: Strings are immutable in Python - it doesn't modify the string in the list.

edited Jun 19 '14 at 18:17

answered Jun 19 '14 at 18:07

Andrew_CS

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if there is a way to do it without converting to lower/uppercase that would be useful as when you convert back you loose the correct case. – DavidJB Jun 19 '14 at 18:08
1

Strings are immutable – Andrew_CS Jun 19 '14 at 18:08
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What do you mean "convert back"? The code shown preserves item? – MrAlias Jun 19 '14 at 18:09
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This is the correct answer. @john `"TESTING".lower()` does not change the case of the original `"TESTING"` string. This is impossible, as strings are immutable in Python (they cannot be changed). It creates a NEW string, with all lowercase letters, and compares that instead. – Adam Smith Jun 19 '14 at 18:10
Thanks, I see what it does now. – DavidJB Jun 19 '14 at 18:11
I see why you asked the question now. – Andrew_CS Jun 19 '14 at 18:13
If this or any of the other answered solved your issue then please accept it so it doesn't remain unanswered. Happy programming! – Andrew_CS Jun 19 '14 at 18:27
That last statement is hand-wavy, though. List indices are mutable, and the OP was concerned with changing the original list. – Jossie Calderon Jun 06 '20 at 09:01

Adam Smith · Answer 2 · 2014-06-19T18:20:32.627

5

If for some reason you REALLY need to compare case insensitive strings (rather than generating a same-case string) you can use regular expressions with the re.IGNORECASE flag. This is a terrible idea for what you seem to be trying to do, but the code is:

import re

my_list = ['webcam', 'home', 'Space', 'Maybe later', 'Webcamnew']
for item in my_list:
    if re.match("webcam$",item, flags=re.I): # re.I == re.IGNORECASE
        print item

The reason this is a Bad Idea is that using regular expressions for simple matching is kind of like using a backhoe to dig post holes. Sure, you can do it, but it's expensive, time-consuming, and has the opportunity to introduce errors you didn't think about until you accidentally swung the boom through your living room window.

edited Jun 19 '14 at 18:20

answered Jun 19 '14 at 18:13

Adam Smith

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If you want to do this, you will need to use `re.escape()` and append a `$`. – Greg Hewgill Jun 19 '14 at 18:15
+1 for alternative route w/ warning – Andrew_CS Jun 19 '14 at 18:16
@GregHewgill why would you need to do `re.escape()`? You're right about `$` though, adding that now. – Adam Smith Jun 19 '14 at 18:18
@AdamSmith: Well you wouldn't need it for a literal `"webcam"`, but you would need it if you're searching for something taken from user input, for example. A string like `"foo[bar"` is an invalid regex. – Greg Hewgill Jun 19 '14 at 18:28
@GregHewgill understood. I don't know if that's part of what the OP needs though, as his example is matching against a literal string. If so it'd be easier to do `re.match("\b"+re.escape(raw_input())+"\b", " ".join(my_list), re.I)` – Adam Smith Jun 19 '14 at 18:30

Match string in python regardless of upper and lower case differences

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