How to find the Cross-section of Pandas Data frame?
Last Updated :
25 Oct, 2020
Sometimes we need to find the cross-section of pandas series or data frame. Here cross-section means getting values at the specified index, values at several indexes, values at several indexes and levels or values at the specified column and axis etc. There is a function known as pandas.DataFrame.xs() which will help in this condition.
pandas.DataFrame.xs() takes a key argument in order to select data at the particular level in MultiIndex and returns cross-section from pandas data frame.
Syntax: DataFrame.xs(key, axis=0, level=None, drop_level=True)
Parameters:
key – Label contained in the index, or partially in a MultiIndex.
axis – Axis to retrieve cross-section on.
level – In case of a key partially contained in a MultiIndex, indicate which levels are used.
drop_level – If False, returns an object with the same levels as self.
Returns:
Cross-section from the original DataFrame
Below is the pandas code which will help in the proper understanding of pandas.DataFrame.xs() function.
Python3
import pandas as pd
animal_dict = {'num_of_legs': [4, 0, 4, 2, 2, 2],
'num_of_wings': [0, 0, 0, 2, 2, 2],
'class': ['Reptiles', 'Reptiles', 'Reptiles',
'Birds', 'Birds', 'Birds'],
'animal': ['Turtle', 'Snake', 'Crocodile',
'Parrot', 'Owl', 'Hummingbird'],
'locomotion': ['swim_walk', 'swim_crawl', 'swim_walk',
'flies', 'flies', 'flies']}
df = pd.DataFrame(data=animal_dict)
df = df.set_index(['class', 'animal', 'locomotion'])
df
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Output:
Example 1: Getting values at a specific index
Output:
Example 2: Getting values at several indexes
Python3
df.xs(('Birds', 'Parrot'))
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Output:
Example 3: Getting values at the specified index and level
Python3
df.xs('Crocodile', level = 1)
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Output:
Example 4: Getting values at several indexes and levels
Python3
df.xs(('Birds', 'flies'),
level=[0, 'locomotion'])
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Output:
Example 5: Getting values at the specified column and axis
Python3
df.xs('num_of_wings', axis=1)
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Output:
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