You can use the following syntax to count the occurrences of a specific value in a column of a pandas DataFrame:
df['column_name'].value_counts()[value]
Note that value can be either a number or a character.
The following examples show how to use this syntax in practice.
Example 1: Count Occurrences of String in Column
The following code shows how to count the number of occurrences of a specific string in a column of a pandas DataFrame:
import pandas as pd #create DataFrame df = pd.DataFrame({'team': ['A', 'A', 'B', 'B', 'B', 'B', 'C', 'C'], 'points': [25, 12, 15, 14, 19, 23, 25, 29], 'assists': [5, 7, 7, 9, 12, 9, 9, 4], 'rebounds': [11, 8, 10, 6, 6, 5, 9, 12]}) #count occurrences of the value 'B' in the 'team' column df['team'].value_counts()['B'] 4
From the output we can see that the string ‘B’ occurs 4 times in the ‘team’ column.
Note that we can also use the following syntax to find how frequently each unique value occurs in the ‘team’ column:
#count occurrences of every unique value in the 'team' column
df['team'].value_counts()
B 4
A 2
C 2
Name: team, dtype: int64
Example 2: Count Occurrences of Numeric Value in Column
The following code shows how to count the number of occurrences of a numeric value in a column of a pandas DataFrame:
import pandas as pd #create DataFrame df = pd.DataFrame({'team': ['A', 'A', 'B', 'B', 'B', 'B', 'C', 'C'], 'points': [25, 12, 15, 14, 19, 23, 25, 29], 'assists': [5, 7, 7, 9, 12, 9, 9, 4], 'rebounds': [11, 8, 10, 6, 6, 5, 9, 12]}) #count occurrences of the value 9 in the 'assists' column df['assists'].value_counts()[9] 3
From the output we can see that the value 9 occurs 3 times in the ‘assists’ column.
We can also use the following syntax to find how frequently each unique value occurs in the ‘assists’ column:
#count occurrences of every unique value in the 'assists' column
df['assists'].value_counts()
9 3
7 2
5 1
12 1
4 1
Name: assists, dtype: int64
From the output we can see:
- The value 9 occurs 3 times.
- The value 7 occurs 2 times.
- The value 5 occurs 1 time.
And so on.
Additional Resources
The following tutorials explain how to perform other common operations in pandas:
How to Count Unique Values in Pandas
How to Count Missing Values in a Pandas
How to Count Observations by Group in Pandas