How can I count number of columns whose name starts with specific words?

Counting the number of columns in a DataFrame whose names start with specific words is a common task for data analysis and manipulation. In Python, you can use the str.startswith() method and the sum() function to accomplish this task.

Get the First and Last Column Names

To return an array containing the names of the first and last columns that start with a specific word, you can use the following code:

df.columns[df.columns.str.startswith('Name_')][[0,-1]]

In this code:

• df.columns represents the collection of column names in the DataFrame.
• df.columns.str.startswith('Name_') filters the column names to include only those that start with 'Name_'.
• [[0,-1]] extracts the first and last elements from the filtered column names.

Count the Number of Columns

To count the number of columns that start with a specific word, you can use the following code:

df.columns.str.startswith('Name_').sum()

In this code:

• df.columns.str.startswith('Name_') filters the column names to include only those that start with 'Name_'.
• .sum() calculates the sum of the filtered column names, which is equivalent to counting the number of columns that satisfy the condition.

Example

Consider the following DataFrame:

   Name_1   Name_2   Age   City
0     John     Jane    20    New York
1     Mark     Emily   25    Los Angeles
2     Tom       Lily    30    San Francisco

To get the first and last column names that start with 'Name_', you can use the following code:

df.columns[df.columns.str.startswith('Name_')][[0,-1]]

The output of this code will be:

Index(['Name_1', 'Name_2'], dtype='object')

To count the number of columns that start with 'Name_', you can use the following code:

df.columns.str.startswith('Name_').sum()

The output of this code will be:

2

Conclusion

Using the str.startswith() method and the sum() function, you can easily count the number of columns in a DataFrame whose names start with specific words. This technique is useful for various data analysis and manipulation tasks.