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# Getting index of value in Series in Pandas

schedule Aug 12, 2023
Last updated
local_offer
PythonPandas
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# Series Index

## Unique case

To get the index of a value in a Series:

``` s = pd.Series([7,4,5,6], index=["a","b","c","d"])s[s == 5] # returns a Series c 5dtype: int64 ```

## Duplicate case

For the duplicate case:

``` s = pd.Series([7,4,5,5], index=["a","b","c","d"])s[s == 5] c 5d 5dtype: int64 ```

## Non-existent case

When the value you are finding does not exist, you get an empty Series:

``` s = pd.Series([7,4,5,6], index=["a","b","c","d"])s[s == 8] Series([], dtype: int64) ```

# Integer Index

## Unique case

To get the integer index of a value in a Series, first convert the Series into an `Index`, and then use the `get_loc(~)` method:

``` s = pd.Series([7,4,5,6], index=["a","b","c","d"])pd.Index(s).get_loc(5) 2 ```

## Duplicate case

When there are duplicates, we get a NumPy array of booleans where `True` indicates the location of the value:

``` s = pd.Series([7,4,5,5], index=["a","b","c","d"])pd.Index(s).get_loc(5) array([False, False, True, True]) ```

If you want a list of integer indices instead of this boolean mask, use NumPy's `where(~)` method instead:

``` s = pd.Series([7,4,5,5], index=["a","b","c","d"])np.where(s==5) (array([2, 3]),) ```

## Non-existent case

If the value does not exist, we get a `KeyError`:

``` s = pd.Series([7,4,5,6], index=["a","b","c","d"])pd.Index(s).get_loc(9) KeyError: 9 ```
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