df.columns.tolist() to return strings not tuples

Question

in pandas to find the columns of a df you do:

df.columns which returns a multiindex array.

If you want to add it to a variable you do:

columns=df.columns.tolist()

which would create a tuple for every columns name

e.g columns=[('A'),('B'),...]

is there a way to create the variable columns with each column as a string item of the list instead of a tuple item of the list or do you just have to do some list editing afterwards?

Answer 1

If you have a multiindex, it's not always clear that tolist() would produce a list of single strings, since it's possible there are, well, multiple indexes.

However, as suggested by @jezreal in the comments, you can select the first level like so:

df.columns.get_level_values(0).tolist()

This can have duplicates since it gets the first level for every column. If instead, you want to select the possible values for level 0 (The "unique" values), you could use

df_multiindex.columns.levels[0].tolist()

Example:

import pandas as pd
from io import StringIO

# Create Example Data
df_multiindex = pd.read_csv(StringIO(
'''Fruit,Color,Count,Price
Apple,Red,3,$1.29
Apple,Green,9,$0.99
Pear,Red,25,$2.59
Pear,Green,26,$2.79
Lime,Green,99,$0.39''')).set_index(['Fruit', 'Color']).T

# Print result
print('get_level_values(0): {}'.format(df_multiindex.columns.get_level_values(0).tolist()))
print('levels[0]:           {}'.format(df_multiindex.columns.levels[0].tolist()))

Output:

get_level_values(0): ['Apple', 'Apple', 'Pear', 'Pear', 'Lime']
levels[0]:           ['Apple', 'Lime', 'Pear']