Pandas Series: searchsorted() function

Last update on September 15 2022 12:55:23 (UTC/GMT +8 hours)

Find indices where elements should be inserted to maintain order

The searchsorted() function is used to find indices where elements should be inserted to maintain order.

Find the indices into a sorted Series self such that, if the corresponding elements in value were inserted before the indices, the order of self would be preserved.

Syntax:

Series.searchsorted(self, value, side='left', sorter=None)

Name	Description	Type/Default Value	Required / Optional
value	Values to insert into self.	array_like	Required
side	If ‘left’, the index of the first suitable location found is given. If ‘right’, return the last such index. If there is no suitable index, return either 0 or N (where N is the length of self).	{‘left’, ‘right’}	Optional
sorter	Optional array of integer indices that sort self into ascending order. They are typically the result of np.argsort.	1-D array_like	Optional

Returns: int or array of int- A scalar or array of insertion points with the same shape as value. Changed in version 0.24.0: If value is a scalar, an int is now always returned. Previously, scalar inputs returned an 1-item array for Series and Categorical.

Notes:

Binary search is used to find the required insertion points.

Example:

Python-Pandas Code:

import numpy as np
import pandas as pd
x = pd.Series([2, 3, 4])
x

Output:

0    2
1    3
2    4
dtype: int64

Python-Pandas Code:

import numpy as np
import pandas as pd
x = pd.Series([2, 3, 4])
x.searchsorted(3)

Output:

Python-Pandas Code:

import numpy as np
import pandas as pd
x = pd.Series([2, 3, 4])
x.searchsorted([2, 4])

Output:

array([0, 2], dtype=int64)

Python-Pandas Code:

import numpy as np
import pandas as pd
x = pd.Series([2, 3, 4])
x.searchsorted([2, 3], side='left')

Output:

array([0, 1], dtype=int64)

Python-Pandas Code:

import numpy as np
import pandas as pd
x = pd.Series([2, 3, 4])
x.searchsorted([2, 3], side='right')

Output:

array([1, 2], dtype=int64)

Python-Pandas Code:

import numpy as np
import pandas as pd
x = pd.Categorical(['tea', 'bread', 'butter', 'milk'], ordered=True)
x.searchsorted('butter')

Output:

Python-Pandas Code:

import numpy as np
import pandas as pd
x = pd.Categorical(['tea', 'bread', 'butter', 'milk'], ordered=True)
x.searchsorted(['bread'], side='right')

Output:

array([2], dtype=int64)

Previous: Explode list-likes including lists, tuples, Series, and np.ndarray
Next: Repeat elements of a Pandas series