Python String lower() method converts a string object into a lower case string. This is one of the builtin string functions in Python. Since strings are immutable in Python, this method only returns a copy of the original string.

Syntax and Usage of Python String lower() Method

Format:

str_copy = str_orig.lower()

Here, str_copy is the lowercase string of str_orig.

a = "HELLO FROM ASKPYTHON"

b = a.lower()

print(a)
print(b)

Output

HELLO FROM ASKPYTHON
hello from askpython

This will make the entire output string lowercase, even if only a part of the input string was uppercase.

a = "Hello from AskPython"
b = a.lower()

print(a)
print(b)

Output

Hello from AskPython
hello from askpython

Since any string literal is handled as a Unicode by Python3, it can lowercase different languages too.

>>> string = 'Километр'
>>> string
'Километр'
>>> string.lower()
'километр'

Pandas module – lower()

There is a lower() method in the Pandas module as well, which has the same functionality as the native Python method, but is for Pandas Objects.

Format:

pandas_copy = pandas_object.str.lower()

Here is an example illustrating the same:

>>> import pandas as pd
>>> 
>>> s = pd.Series(['Hello', 'from', 'ASKPYTHON'])
>>> print(s)
0        Hello
1         from
2    ASKPYTHON
dtype: object
>>> 
>>> print(s.str.lower())
0        hello
1         from
2    askpython
dtype: object
>>> print(s)
0        Hello
1         from
2    ASKPYTHON
dtype: object

As you can observe, the original object remains unchanged, and we get a new object with all lowercase strings!

References

• Python Documentation on str.lower()
• StackOverflow Question