Renaming columns in pandas

Question

I have a DataFrame using pandas and column labels that I need to edit to replace the original column labels.

I'd like to change the column names in a DataFrame A where the original column names are:

['$a', '$b', '$c', '$d', '$e'] 

to

['a', 'b', 'c', 'd', 'e'].

I have the edited column names stored it in a list, but I don't know how to replace the column names.

Answer 1

df = pd.DataFrame({'$a': [1], '$b': [1], '$c': [1], '$d': [1], '$e': [1]})

If your new list of columns is in the same order as the existing columns, the assignment is simple:

new_cols = ['a', 'b', 'c', 'd', 'e']
df.columns = new_cols
>>> df
   a  b  c  d  e
0  1  1  1  1  1

If you had a dictionary keyed on old column names to new column names, you could do the following:

d = {'$a': 'a', '$b': 'b', '$c': 'c', '$d': 'd', '$e': 'e'}
df.columns = df.columns.map(lambda col: d[col])  # Or `.map(d.get)` as pointed out by @PiRSquared.
>>> df
   a  b  c  d  e
0  1  1  1  1  1

If you don't have a list or dictionary mapping, you could strip the leading $ symbol via a list comprehension:

df.columns = [col[1:] if col[0] == '$' else col for col in df]

Answer 2

Real simple just use

df.columns = ['Name1', 'Name2', 'Name3'...]

and it will assign the column names by the order you put them

Answer 3

Use the df.rename() function and refer the columns to be renamed. Not all the columns have to be renamed:

df = df.rename(columns={'oldName1': 'newName1', 'oldName2': 'newName2'})
# Or rename the existing DataFrame (rather than creating a copy) 
df.rename(columns={'oldName1': 'newName1', 'oldName2': 'newName2'}, inplace=True)

Answer 4

Another way we could replace the original column labels is by stripping the unwanted characters (here '$') from the original column labels.

This could have been done by running a for loop over df.columns and appending the stripped columns to df.columns.

Instead , we can do this neatly in a single statement by using list comprehension like below:

df.columns = [col.strip('$') for col in df.columns]

(strip method in Python strips the given character from beginning and end of the string.)