pandas rename multiple columns

1for j in range(len(df.columns)):
2    old = df.columns[j]
3    new = new_columns[j]
4    df = df.rename(columns = {old:new})

1# df is a pandas DataFrame
2
3for col_name in df.columns:
4  # you can specify conditions if you need 
5  # to change the name of some column only
6  df = df.rename(columns = {col_name:new_col_name}