Otherwise, simply return the value using a lambda function. If it is a string, then convert it to lowercase using the lower() method before returning it.Check if the value represents a string value using the isinstance() method.However, the casefold() method will convert it to ‘ ss‘.Īußen Method 3: Using map+ lambda+ isinstance The lower() method will not be able to convert this to the lowercase equivalent. For example, the lowercase letter 'ß' in German is equivalent to ‘ ss‘. The casefold() method is similar to the lower() method, but the casefold() method exhibits a more aggressive and stronger behavior than the lower() method. Str.casefold() is a built-in method in Python that returns a string where all the characters of the returned string are lowercased. The only difference in this case is we will be using the str.casefold() method instead of the lower() method. The idea here is quite similar to str.lowercase() method. Recap to str.lower(): Returns a lowercase version of the given string. To select a column, use the square bracket notation and specify the column name within it, for example, df. Method 1: Using str.lower()Īpproach: Call the str.lower() function upon the column to change its string values to lowercase. Let’s dive into the different approaches that will help us to convert the upper case strings in the DataFrame to lowercase. When you change a pandas DataFrame string column to lowercase, then the column is returned such that every string in the column is converted and displayed in lowercase while any non-alphabetical characters remain the same as seen in the above-expected output. You can test this code in any online Python sandbox.Problem: Given a Pandas DataFrame how to change the strings in the DataFrame to lowercase?Įxample: Consider the following Pandas DataFrame: import pandas as pd This method not only converts all uppercase letters of the Latin alphabet into lowercase ones, but also shows how such logic is implemented. So in Python 2, Unicode can encode into Python strings, and Python strings can decode into the Unicode type. However, to get the lowercase back in type str, encode the python string to utf-8 again: > print string Software should only work with Unicode strings internally, converting to a particular encoding on output. It is recommended that you always work with text in Unicode. > unicode_from_string = string_to_unicode = unicode_literalīoth methods convert to the unicode type - and same as the unicode_literal. We can either use the unicode constructor or str.decode method with the codec to convert the str to unicode: > unicode_from_string = unicode(string, 'utf-8') # "encoding" unicode from string Python's Unicode type is a universal encoding format that has many advantages relative to most other encodings. Now if we only have it in the form of a str, we need to convert it to unicode. Note that the bytes are completely different from the str bytes - the escape character is '\u' followed by the 2-byte width, or 16 bit representation of these unicode letters: > unicode_literal So we need a unicode string to handle this conversion, accomplished easily with a unicode string literal, which disambiguates with a u prefix (and note the u prefix also works in Python 3): > unicode_literal = u'Километр' For more on that, see the Unicode how-to in the docs and PEP 263 Use Unicode literals, not str literals In scripts, Python will object to non-ascii (as of Python 2.5, and warning in Python 2.4) bytes being in a string with no encoding given, since the intended coding would be ambiguous. In Python 2, the below, pasted into a shell, encodes the literal as a string of bytes, using utf-8.Īnd lower doesn't map any changes that bytes would be aware of, so we get the same string. Python 2, plain string literals are bytes Python 3 handles plain string literals as unicode: > string = 'Километр' This is a str method in Python 3, but in Python 2, you'll want to look at the PyICU or py2casefold - several answers address this here. However, if the purpose is to do case insensitive matching, you should use case-folding: > 'Kilometers'.casefold() The canonical Pythonic way of doing this is > 'Kilometers'.lower()
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