Python Pandas - Identifying the index of first matching value in a Dataframe column

Question

So far I am getting the index of first matching record for a particular value in the Python data frame column. I get it using the code below :

df1.loc[df1.Column1 == 'word1'].index.tolist()[0]

Suppose if 'word1' is present four times in the data frame for example in the index positions : 3, 7, 9, 14, the above command will return me the answer as 3

Now I need to check the same with multiple values for the column and the output should be the first matching index of any of those values.

I tried with few options as shown below but in vain.

df1.loc[df1.Column1 == 'word1'|'word2'].index.tolist()[0]
df1.loc[df1.Column1 == 'word1','word2'].index.tolist()[0]
df1.loc[df1.Column1 == 'word1' or 'word2'].index.tolist()[0]

Any idea on how to check for multiple values here ?

jezrael · Accepted Answer · 2017-09-26 13:50:07Z

3

You need isin for condition:

df1.loc[df1.Column1.isin(['word1','word2'])].index.tolist()[0]

Simplier solution with idxmax for get index of first max value, because Trues are handle like 1s:

print (df1.Column1.isin(['word1','word2']))
0    False
1    False
2    False
3     True
4    False
5    False
6     True
7    False
Name: Column1, dtype: bool

df1.Column1.isin(['word1','word2']).idxmax()

Or with numpy.where:

np.where(df1.Column1.isin(['word1','word2']))[0][0]

Sample:

df1 = pd.DataFrame({ 'Column1':['s','g','h','word2','d','f','word1','d']})

a = df1.Column1.isin(['word1','word2']).idxmax()
print (a)
3

edited Sep 26, 2017 at 13:50

answered Sep 26, 2017 at 13:41

jezrael

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2 Comments

JKC Over a year ago

Thank you so much. But can you please shed more light on idxmax. By its name I assume there must be something called idxmin as well.

jezrael Over a year ago

Yes, df1.Column1.isin(['word1','word2']).idxmin() return first False index, test it by df1 = pd.DataFrame({ 'Column1':['word2','g','h','word2','d','f','word1','d']})

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