Number of Observations

There are several aggregate functions in pandas. One of them is .count() method, which counts number of non-null observation for each column.


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# Importing library
import pandas as pd

# Reading csv file
df = pd.read_csv('https://codefinity-content-media.s3.eu-west-1.amazonaws.com/67798cef-5e7c-4fbc-af7d-ae96b4443c0a/audi.csv')
# Count number of non-null rows
print(df.count())

This method is popular for counting number of rows under specific condition. For example, you may count number of cars manufactured after 2015. This time you don't need to see the number of observation in each column, so you can choose particular one.


              1234567
            
# Importing library
import pandas as pd

# Reading csv file
df = pd.read_csv('https://codefinity-content-media.s3.eu-west-1.amazonaws.com/67798cef-5e7c-4fbc-af7d-ae96b4443c0a/audi.csv')
# Count number of cars manufactured after 2015
print(df.loc[df.year > 2015, 'model'].count())

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Sezione 4. Capitolo 1

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Contenuti del Corso

Introduction to pandas [track]

Number of Observations

There are several aggregate functions in pandas. One of them is .count() method, which counts number of non-null observation for each column.


              1234567
            
# Importing library
import pandas as pd

# Reading csv file
df = pd.read_csv('https://codefinity-content-media.s3.eu-west-1.amazonaws.com/67798cef-5e7c-4fbc-af7d-ae96b4443c0a/audi.csv')
# Count number of non-null rows
print(df.count())


              1234567
            
# Importing library
import pandas as pd

# Reading csv file
df = pd.read_csv('https://codefinity-content-media.s3.eu-west-1.amazonaws.com/67798cef-5e7c-4fbc-af7d-ae96b4443c0a/audi.csv')
# Count number of cars manufactured after 2015
print(df.loc[df.year > 2015, 'model'].count())

Tutto è chiaro?

Grazie per i tuoi commenti!

Sezione 4. Capitolo 1