Python | Pandas Index.where

Pandas Index is an immutable ndarray implementing an ordered, sliceable set. It is the basic object which stores the axis labels for all pandas objects.

Pandas Index.where function return an Index of same shape as self and whose corresponding entries are from self where cond is True and otherwise are from other.

Syntax: Index.where(cond, other=None)

Parameter :
cond : boolean array-like with the same length as self
other : scalar, or array-like

Returns : Index

Example #1: Use Index.where function to return an Index, in which we select the value from the other Index if value of this Index is not smaller than 100.

# importing pandas as pd
import pandas as pd

# Creating the first index
idx1 = pd.Index([900, 45, 21, 145, 38, 422])

# Creating the second index
idx2 = pd.Index([1100, 1200, 1300, 1400, 1500, 1600])

# Print the first index
print(idx1)

# Print the second index
print(idx2)

Output :

Now we will use Index.where function to return an Index, in which we select the value from the other Index if value of this Index is not smaller than 100.

# return the new index based on the condition
result = idx1.where(idx1 < 100, idx2)

# Print the result
print(result)

Output :

As we can see in the output, the Index.where function has successfully returned an Index object satisfying the passed condition.

Example #2 : Use Index.where function to return an Index, which satisfy the passed condition.

# importing pandas as pd
import pandas as pd

# Creating the first index
idx1 = pd.Index([900, 45, 21, 145, 38, 422])

# Creating the second index
idx2 = pd.Index([1100, 1200, 1300, 1400, 1500, 1600])

# Print the first index
print(idx1)

# Print the second index
print(idx2)

Output :

Now we will use Index.where function to return an Index, in which we select the value from the other Index if value of other Index minus 1200 is not smaller than idx1.

# return the new index based on the condition
result = idx1.where((idx2 - 1200) < idx1, idx2)

# Print the result
print(result)

Output :

As we can see in the output, the Index.where function has successfully returned an Index object satisfying the passed condition.