How to use apply() In Python Pandas
If we want to get a count of all columns across all columns, then we have to use apply() function. In that we will use value_counts() method.
Syntax:
data.apply(pd.value_counts)
Example: Get count of all columns across all columns
Python3
# import pandas module import pandas as pd # create a dataframe # with 5 rows and 4 columns data = pd.DataFrame({ 'name' : [ 'sravan' , 'bobby' , 'sravan' , 'sravan' , 'ojaswi' ], 'subjects' : [ 'java' , 'php' , 'java' , 'html/css' , 'python' ], 'marks' : [ 98 , 90 , 78 , 91 , 87 ], 'age' : [ 11 , 23 , 23 , 21 , 21 ] }) # get all count data. apply (pd.value_counts) |
Output:
How to Count Occurrences of Specific Value in Pandas Column?
In this article, we will discuss how to count occurrences of a specific column value in the pandas column.
Dataset in use:
We can count by using the value_counts() method. This function is used to count the values present in the entire dataframe and also count values in a particular column.
Syntax: data[‘column_name’].value_counts()[value]
where
- data is the input dataframe
- value is the string/integer value present in the column to be counted
- column_name is the column in the dataframe
Example: To count occurrences of a specific value
Python3
# import pandas module import pandas as pd # create a dataframe # with 5 rows and 4 columns data = pd.DataFrame({ 'name' : [ 'sravan' , 'ojsawi' , 'bobby' , 'rohith' , 'gnanesh' , 'sravan' , 'sravan' , 'ojaswi' ], 'subjects' : [ 'java' , 'php' , 'java' , 'php' , 'java' , 'html/css' , 'python' , 'R' ], 'marks' : [ 98 , 90 , 78 , 91 , 87 , 78 , 89 , 90 ], 'age' : [ 11 , 23 , 23 , 21 , 21 , 21 , 23 , 21 ] }) # count values in name column print (data[ 'name' ].value_counts()[ 'sravan' ]) # count values in subjects column print (data[ 'subjects' ].value_counts()[ 'php' ]) # count values in marks column print (data[ 'marks' ].value_counts()[ 89 ]) |
Output:
3
2
1
If we want to count all values in a particular column, then we do not need to mention the value.
Syntax:
data['column_name'].value_counts()
Example: To count the occurrence of a value in a particular column
Python3
# import pandas module import pandas as pd # create a dataframe # with 5 rows and 4 columns data = pd.DataFrame({ 'name' : [ 'sravan' , 'ojsawi' , 'bobby' , 'rohith' , 'gnanesh' , 'sravan' , 'sravan' , 'ojaswi' ], 'subjects' : [ 'java' , 'php' , 'java' , 'php' , 'java' , 'html/css' , 'python' , 'R' ], 'marks' : [ 98 , 90 , 78 , 91 , 87 , 78 , 89 , 90 ], 'age' : [ 11 , 23 , 23 , 21 , 21 , 21 , 23 , 21 ] }) # count all values in name column print (data[ 'name' ].value_counts()) # count all values in subjects column print (data[ 'subjects' ].value_counts()) # count all values in marks column print (data[ 'marks' ].value_counts()) # count all values in age column print (data[ 'age' ].value_counts()) |
Output:
If we want to get the results in order (like ascending and descending order), we have to specify the parameter
Syntax:
Ascending order:
data[‘column_name’].value_counts(ascending=True)
Descending Order:
data[‘column_name’].value_counts(ascending=False)
Example: To get results in an ordered fashion
Python3
# import pandas module import pandas as pd # create a dataframe # with 5 rows and 4 columns data = pd.DataFrame({ 'name' : [ 'sravan' , 'ojsawi' , 'bobby' , 'rohith' , 'gnanesh' , 'sravan' , 'sravan' , 'ojaswi' ], 'subjects' : [ 'java' , 'php' , 'java' , 'php' , 'java' , 'html/css' , 'python' , 'R' ], 'marks' : [ 98 , 90 , 78 , 91 , 87 , 78 , 89 , 90 ], 'age' : [ 11 , 23 , 23 , 21 , 21 , 21 , 23 , 21 ] }) # count all values in name column in ascending order print (data[ 'name' ].value_counts(ascending = True )) # count all values in subjects column in ascending order print (data[ 'subjects' ].value_counts(ascending = True )) # count all values in marks column in descending order print (data[ 'marks' ].value_counts(ascending = False )) # count all values in age column in descending order print (data[ 'age' ].value_counts(ascending = False )) |
Output: