Count all rows or those that satisfy some condition in Pandas dataframe

Let’s see how to count number of all rows in a Dataframe or rows that satisfy a condition in Pandas.

1) Count all rows in a Pandas Dataframe using Dataframe.shape.

Dataframe.shape returns tuple of shape (Rows, columns) of dataframe/series.

Let’s create a pandas dataframe.

# import pandas library as pd
import pandas as pd

# List of Tuples
students = [('Ankit', 22, 'Up', 'Geu'),
           ('Ankita', 31, 'Delhi', 'Gehu'),
           ('Rahul', 16, 'Tokyo', 'Abes'),
           ('Simran', 41, 'Delhi', 'Gehu'),
           ('Shaurya', 33, 'Delhi', 'Geu'),
           ('Harshita', 35, 'Mumbai', 'Bhu' ),
           ('Swapnil', 35, 'Mp', 'Geu'),
           ('Priya', 35, 'Uk', 'Geu'),
           ('Jeet', 35, 'Guj', 'Gehu'),
           ('Ananya', 35, 'Up', 'Bhu')
            ]

# Create a DataFrame object from
# list of tuples with columns
# and indices.
details = pd.DataFrame(students, columns =['Name', 'Age',
                                           'Place', 'College'],
                        index =['a', 'b', 'c', 'd', 'e',
                                'f', 'g', 'i', 'j', 'k'])

details

Output:

Code: Count all rows

# import pandas library as pd
import pandas as pd

# List of Tuples
students = [('Ankit', 22, 'Up', 'Geu'),
           ('Ankita', 31, 'Delhi', 'Gehu'),
           ('Rahul', 16, 'Tokyo', 'Abes'),
           ('Simran', 41, 'Delhi', 'Gehu'),
           ('Shaurya', 33, 'Delhi', 'Geu'),
           ('Harshita', 35, 'Mumbai', 'Bhu' ),
           ('Swapnil', 35, 'Mp', 'Geu'),
           ('Priya', 35, 'Uk', 'Geu'),
           ('Jeet', 35, 'Guj', 'Gehu'),
           ('Ananya', 35, 'Up', 'Bhu')
            ]

# Create a DataFrame object from
# list of tuples with columns
# and indices.
details = pd.DataFrame(students, columns =['Name', 'Age',
                                           'Place', 'College'],
                        index =['a', 'b', 'c', 'd', 'e',
                                'f', 'g', 'i', 'j', 'k'])

# 0th index of tuple returned by shape
# attribute give the number
# of rows in a given dataframe
num_rows = details.shape[0]

print('Number of Rows in given dataframe : ',
      num_rows)

Output:

Number of Rows in given dataframe :  10

2) Count all rows in a Pandas Dataframe using Dataframe.index.

Dataframe.index attribute gives a sequence of index or row labels.

Code:

import pandas as pd

# List of Tuples
students = [('Ankit', 22, 'Up', 'Geu'),
           ('Ankita', 31, 'Delhi', 'Gehu'),
           ('Rahul', 16, 'Tokyo', 'Abes'),
           ('Simran', 41, 'Delhi', 'Gehu'),
           ('Shaurya', 33, 'Delhi', 'Geu'),
           ('Harshita', 35, 'Mumbai', 'Bhu' ),
           ('Swapnil', 35, 'Mp', 'Geu'),
           ('Priya', 35, 'Uk', 'Geu'),
           ('Jeet', 35, 'Guj', 'Gehu'),
           ('Ananya', 35, 'Up', 'Bhu')
            ]

# Create a DataFrame object from
# list of tuples with columns
# and indices.
details = pd.DataFrame(students, columns =['Name', 'Age',
                                           'Place', 'College'],
                        index =['a', 'b', 'c', 'd', 'e',
                                'f', 'g', 'i', 'j', 'k'])

# count number of rows in given dataframe
# by finding the length of indices
num_rows = len(details.index)

print('Number of Rows in given dataframe : ',
      num_rows)

Output:

Number of Rows in given dataframe :  10

3) Count rows in a Pandas Dataframe that satisfies a condition using Dataframe.apply().

Dataframe.apply(), apply function to all the rows of a dataframe to find out if elements of rows satisfies a condition or not, Based on the result it returns a bool series.

Code:

# import pandas library as pd
import pandas as pd

# List of Tuples
students = [('Ankit', 22, 'Up', 'Geu'),
           ('Ankita', 31, 'Delhi', 'Gehu'),
           ('Rahul', 16, 'Tokyo', 'Abes'),
           ('Simran', 41, 'Delhi', 'Gehu'),
           ('Shaurya', 33, 'Delhi', 'Geu'),
           ('Harshita', 35, 'Mumbai', 'Bhu' ),
           ('Swapnil', 35, 'Mp', 'Geu'),
           ('Priya', 35, 'Uk', 'Geu'),
           ('Jeet', 35, 'Guj', 'Gehu'),
           ('Ananya', 35, 'Up', 'Bhu')
            ]

# Create a DataFrame object from
# list of tuples with columns
# and indices.
details = pd.DataFrame(students, columns =['Name', 'Age',
                                           'Place', 'College'],
                        index =['a', 'b', 'c', 'd', 'e',
                                'f', 'g', 'i', 'j', 'k'])

# Get a bool series representing which row
# satisfies the condition i.e. True for
# row in which 'College' is 'Geu'
details = details.apply(lambda x : True
            if x['College'] == "Geu" else False, axis = 1)

# Count number of True in the series
num_rows = len(details[details == True].index)

print('Number of Rows in dataframe in which College is Geu : ',
      num_rows )

Output:

Number of Rows in dataframe in which College is Geu :  4