How to change the column names from a tuple to string?

Question

I have used pd.pivot_table in pandas dataframe, and the column names becomes tuples like ('A1', 'B1'), ('A1', 'B2'), ..., and I want them to be like 'A1_B1', 'A1_B2', ...

I tried to use df.columns.values[i] = df.columns.values[i][0] + '_' + df6.columns.values[i][1], and tried rename as well.

When I checked df.columns.values, the column names changed, but when I cannot use these names to do indexing. I am new to python, so might not know the difference between column names and column indices.

Answer 1

setup

df = pd.DataFrame(
    np.arange(8).reshape(2, 4),
    columns=[('A1', 'B1'), ('A2', 'B1'), ('A1', 'B2'), ('A2', 'B2')])

print(df)

   (A1, B1)  (A2, B1)  (A1, B2)  (A2, B2)
0         0         1         2         3
1         4         5         6         7

rename

df.rename(columns='_'.join, inplace=True)
print(df)

   A1_B1  A2_B1  A1_B2  A2_B2
0      0      1      2      3
1      4      5      6      7

map

df.columns = df.columns.map('_'.join)
print(df)

   A1_B1  A2_B1  A1_B2  A2_B2
0      0      1      2      3
1      4      5      6      7