A NameError usually happens when Python cannot find the variable or column name you referenced.

When sorting a pandas DataFrame, this often occurs if the column name is written without quotes or if the variable does not exist in the current scope.

For example, this will cause a NameError:

df.sort_values(by=column_name)

if column_name is not defined.

Instead, reference the column as a string:

df.sort_values(by="column_name")

Also ensure that:

• The DataFrame (df) exists

• The column name is spelled correctly

• The column actually exists in df.columns

Checking df.columns before sorting can help confirm the correct column name.