Check if a value exists in pandas dataframe index

Question

I am sure there is an obvious way to do this but cant think of anything slick right now   Basically instead of raising exception I would like to get True or False to see if a value exists in pandas df index   import pandas as pd df   pd DataFrame   test   1 2 3 4    index   a   b   c   d    df loc  g       should give False    What I have working now is the following  sum df index     g

User · Answer

Multi index works a little different from single index. Here are some methods for multi-indexed dataframe.

df = pd.DataFrame({'col1': ['a', 'b','c', 'd'], 'col2': ['X','X','Y', 'Y'], 'col3': [1, 2, 3, 4]}, columns=['col1', 'col2', 'col3'])
df = df.set_index(['col1', 'col2'])

in df.index works for the first level only when checking single index value.

'a' in df.index     # True
'X' in df.index     # False

Check df.index.levels for other levels.

'a' in df.index.levels[0] # True
'X' in df.index.levels[1] # True

Check in df.index for an index combination tuple.

('a', 'X') in df.index  # True
('a', 'Y') in df.index  # False

User · Answer

Just for reference as it was something I was looking for  you can test for presence within the values or the index by appending the   values  method  e g   g in df  lt your selected field gt  values g in df index values   I find that adding the   values  to get a simple list or ndarray out makes exist or  in  checks run more smoothly with the other python tools  Just thought I d toss that out there for people

User · Answer

This should do the trick   g  in df index

User · Answer

Code below does not print boolean  but allows for dataframe subsetting by index    I understand this is likely not the most efficient way to solve the problem  but I  1  like the way this reads and  2  you can easily subset where df1 index exists in df2   df3   df1 df1 index isin df2 index     or where df1 index does not exist in df2     df3   df1  df1 index isin df2 index

User · Answer

with DataFrame  df data   gt  gt  gt  df data   id   name  value 0  a  ampha      1 1  b   beta      2 2  c     ce      3   I tried    gt  gt  gt  getattr df data   value   isin  1   any   True  gt  gt  gt  getattr df data   value   isin   1    any   True   but    gt  gt  gt  1 in getattr df data   value   True  gt  gt  gt   1  in getattr df data   value   False   So fun  D

User · Answer

df   pandas DataFrame   g   1    index   isStop      df loc  g    if  g  in df index      print  find g    if  isStop  in df index      print  find a

[python] Check if a value exists in pandas dataframe index

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