python: change column name

>>> df = pd.DataFrame({"A": [1, 2, 3], "B": [4, 5, 6]})
>>> df.rename(columns={"A": "a", "B": "c"})
   a  c
0  1  4
1  2  5
2  3  6

#df.rename() will only return a new df with the new headers
#df = df.rename() will change the heders of the current dataframe 
df = df.rename(columns={"old_col1": "new_col1", "old_col2": "new_col2"})

df = df.rename(columns = {'myvar':'myvar_new'})

print(df.rename(columns={'A': 'a', 'C': 'c'}))
#         a   B   c
# ONE    11  12  13
# TWO    21  22  23
# THREE  31  32  33