Pandas Rename a Single Row of MultiIndex by Tuple

PKB :

I'm trying to rename a single row of a pandas dataframe by it's tuple.

For example:

import pandas as pd
df = pd.DataFrame(data={'i1':[0,0,0,0,1,1,1,1],
                       'i2':[0,1,2,3,0,1,2,3],
                       'x':[1.,2.,3.,4.,5.,6.,7.,8.],
                       'y':[9,10,11,12,13,14,15,16]})
df.set_index(['i1','i2'], inplace=True)

Creates df:

         x   y
i1 i2         
0  0   1.0   9
   1   2.0  10
   2   3.0  11
   3   4.0  12
1  0   5.0  13
   1   6.0  14
   2   7.0  15
   3   8.0  16

I'd like to be able to use something like: df.rename(index={(0,1):(0,9)},inplace=True) to get:

         x   y
i1 i2         
0  0   1.0   9
   9   2.0  10 <-- new key
   2   3.0  11
   3   4.0  12
1  0   5.0  13
   1   6.0  14
   2   7.0  15
   3   8.0  16

The command executes without raising an error but returns the same df unchanged.

This also returns the same df: df.rename(index={pd.IndexSlice[0,1]:pd.IndexSlice[0,9]},inplace=True)

This will have close to the desired effect:

df.loc[(0,9),:] = df.loc[(0,1),:]
df.drop(index=(0,1),inplace=True)

but if row ordering matters, it'll be a pain to get it into the right order, and possibly quite slow if the df gets big.

I'm using Pandas 1.0.1, python 3.7. Any suggestions? Thank you in advance.

jezrael :

Possible solution with list comprehension and MultiIndex.from_tuples:

L = [(0,9) if x == (0,1) else x for x in df.index]
df.index = pd.MultiIndex.from_tuples(L, names=df.index.names)
print (df)
         x   y
i1 i2         
0  0   1.0   9
   9   2.0  10
   2   3.0  11
   3   4.0  12
1  0   5.0  13
   1   6.0  14
   2   7.0  15
   3   8.0  16