Lowercase a string in Python

David Y. —
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The Problem

How do I make a string all lowercase in Python?

The Solution

We can use Python’s built-in str.lower()(https://docs.python.org/3/library/stdtypes.html#str.lower) method. This will work regardless of how many uppercase letters the string contains. For example:

print("HELLO WORLD!".lower())  # will output "hello world!"
print("Hello World!".lower())  # will output "hello world!"
print("hello world!".lower())  # will output "hello world!"

If we’re making our string all lowercase in order to do case-insensitive matching, we may want to use str.casefold() instead. This method is a more aggressive form of str.lower(), which includes additional substitutions such as “ss” for the German character “ß”. The workings of this method are implemented in accordance with section 3.13 of the Unicode Standard.

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