How replace Unnamed header column with previous

[boring_accountant]

Assuming you want to replace all columns containing the string 'Unnamed' with the string 'nan', this will do:

print(df)
df.columns = [col if not 'Unnamed' in col else 'nan' for col in df.columns]
print(df)

Output:
  First  Unnamed: 1  Unnamed: 2
0     A           1           3
1     B           2           4

  First  nan  nan
0     A    1    3
1     B    2    4

As an alternative, the following yields equal results. I'm not sure whichever I prefer but both are possible.

df.columns = df.columns.map(lambda col: col if not 'Unnamed' in col else 'nan')