How can I make pandas dataframe column headers all lowercase?

Question

I want to make all column headers in my pandas data frame lower case

Example

If I have:

data =

  country country isocode  year     XRAT          tcgdp
0  Canada             CAN  2001  1.54876   924909.44207
1  Canada             CAN  2002  1.56932   957299.91586
2  Canada             CAN  2003  1.40105  1016902.00180
....

I would like to change XRAT to xrat by doing something like:

data.headers.lowercase()

So that I get:

  country country isocode  year     xrat          tcgdp
0  Canada             CAN  2001  1.54876   924909.44207
1  Canada             CAN  2002  1.56932   957299.91586
2  Canada             CAN  2003  1.40105  1016902.00180
3  Canada             CAN  2004  1.30102  1096000.35500
....

I will not know the names of each column header ahead of time.

Asked By: natsuki_2002

||

Source

Answer 1

You can do it like this:

data.columns = map(str.lower, data.columns)

or

data.columns = [x.lower() for x in data.columns]

example:

>>> data = pd.DataFrame({'A':range(3), 'B':range(3,0,-1), 'C':list('abc')})
>>> data
   A  B  C
0  0  3  a
1  1  2  b
2  2  1  c
>>> data.columns = map(str.lower, data.columns)
>>> data
   a  b  c
0  0  3  a
1  1  2  b
2  2  1  c

Answered By: Roman Pekar

Answer 2

If you want to do the rename using a chained method call, you can use

data.rename(columns=str.lower)

If you’re not chaining method calls, you can add inplace=True

data.rename(columns=str.lower, inplace=True)

Answered By: theister

Answer 3

You could do it easily with str.lower for columns:

df.columns = df.columns.str.lower()

Example:

In [63]: df
Out[63]: 
  country country isocode  year     XRAT         tcgdp
0  Canada             CAN  2001  1.54876  9.249094e+05
1  Canada             CAN  2002  1.56932  9.572999e+05
2  Canada             CAN  2003  1.40105  1.016902e+06

In [64]: df.columns = df.columns.str.lower()

In [65]: df
Out[65]: 
  country country isocode  year     xrat         tcgdp
0  Canada             CAN  2001  1.54876  9.249094e+05
1  Canada             CAN  2002  1.56932  9.572999e+05
2  Canada             CAN  2003  1.40105  1.016902e+06

Answered By: Anton Protopopov

Answer 4

df.columns = df.columns.str.lower()

is the easiest but will give an error if some headers are numeric

if you have numeric headers then use this:

df.columns = [str(x).lower() for x in df.columns]

Answered By: Chadee Fouad

Answer 5

I noticed some of the other answers will fail if a column name is made of digits (e.g. "123"). Try these to handle such cases too.

Option 1: Use df.rename

def rename_col(old_name):
    return str(old_name).lower()

df.rename(rename_col)

Option 2 (from this comment):

df.columns.astype(str).str.lower()

Answered By: Princy

Answer 6

Another convention based on the official documentation:

frame.rename(mapper=lambda x:x.lower(), axis='columns', inplace=True)

Parameters:
mapper:
Dict-like or function transformations to apply to that axis’ values. Use either mapper and axis to specify the axis to target with mapper, or index and columns.

Answered By: kc12

Answer 7

df.rename(columns = lambda x:x.lower())

add inplace= True for permanent change

df.rename(columns = lambda x:x.lower(), inplace=True )

Answered By: py coder

How can I make pandas dataframe column headers all lowercase?

Question:

Example

Answers: