CODEWITHSUNDEEP
python-3.xpandas
Wouter
Wouter

Reputation: 1326

How to interprete the Pandas Index class documentation?

Please help me read and use the great Pandas documentation better.

E.g.pandas.Index.contains and the overview of attributes and methods for the Pandas Index class.

In this case, I want to check if a key is in the index before applying

dataframe.loc['key',['column']]) # first check if key is in index to avoid KeyError: 'the label [key] is not in the [index]'

I want to use the method contains(key) ("return a boolean if this key is IN the index").

So I incorrectly tried dataframe.Index.contains. But it should be index and not Index. So why is it written with a capital in the documentation?

Also, it should be with .str in between index and contains:

dataframe.index.str.contains('key')) # not dataframe.Index.contains

It is my fault, but how should I know this from the documentation?

Upvotes: 0

Views: 66

Answers (1)

Bharath M Shetty
Bharath M Shetty

Reputation: 30605

If you want to know whether a key is in index then use .isin i.e ("return a boolean array if this key is IN the index")

df= pd.DataFrame([['a','b'],['b','c'],['c','z'],['d','b']])

   0  1
0  a  b
1  b  c
2  c  z
3  d  b

df.index.isin([1,2])

Output: 

array([False,  True,  True, False], dtype=bool)

For a scalar use in i.e. k in df.index where k is any number or scalar

Eg: 

2 in df.index
True 

df.index.isin([2])
array([False, False,  True, False], dtype=bool)

Upvotes: 1

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