Unlocking the Mysteries of Pandas DataFrames: A Guide to Removing Columns and Creating DataFrames
Data is everywhere, and as we continue to generate more and more, effectively managing it has become an essential skill. Fortunately, Python provides us with the Pandas library, which makes data manipulation and analysis more straightforward.
In particular, the DataFrame class makes working with structured, tabular data easier. In this article, we will show you how to remove columns from a DataFrame using three different methods and also walk-through creating and viewing a DataFrame.
Creating a DataFrame
Creating a DataFrame is the first step in working with Pandas. As its name suggests, a DataFrame is a two-dimensional table-like structure that contains rows and columns.
With Pandas, you can create a DataFrame in many ways. The most common method is by passing a dictionary of lists or arrays to the DataFrame constructor.
import pandas as pd
data = {'name': ['Alex', 'Bob', 'Carry'],
'age': [22, 34, 19],
'gender': ['M', 'M', 'F']}
df = pd.DataFrame(data)
print(df)
Output:
name age gender
0 Alex 22 M
1 Bob 34 M
2 Carry 19 F
As you can see, the DataFrame has three columns: name, age, and gender. The index, on the left, begins from 0 and increments by one for each row.
Viewing a DataFrame
Viewing contents of a DataFrame is possible using various functions like .head(), .tail() and .info(), among others. Using .head(), we can view the top five rows of each column, like this:
print(df.head())
Output:
name age gender
0 Alex 22 M
1 Bob 34 M
2 Carry 19 F
As seen above .head() returns the first five rows of the DataFrame. If we don’t pass any argument to the function like this:
print(df.head(2))
Output:
name age gender
0 Alex 22 M
1 Bob 34 M
It will only return the first two rows. On the other hand, to return the last few rows of a DataFrame, we can use the .tail() function.
For instance, let’s return the last two rows of the given DataFrame:
print(df.tail(2))
Output:
name age gender
1 Bob 34 M
2 Carry 19 F
Now that we have created and viewed a DataFrame, let’s learn how to remove columns from one.
Removing Columns in a DataFrame
There are three primary ways to remove columns from a Pandas DataFrame: using drop, iloc, and del. Let’s look at each in more detail.
Method 1: Using drop
The drop method is one of the most common ways of removing a column from a DataFrame. It is a general-purpose function in Pandas that removes rows or columns by a label or sequence of labels.
Here is the general syntax to remove a column using the drop method:
df.drop(['column_name'], axis=1, inplace=True)
column_name: The name of the column to removeaxis: 0 for rows and 1 for columnsinplace: If True, changes will be made to the DataFrame rather than returning a new one
Here’s an example of how to remove the ‘gender’ column from our DataFrame using the drop method:
df.drop(['gender'], axis=1, inplace=True)
print(df)
Output:
name age
0 Alex 22
1 Bob 34
2 Carry 19
As you can see, we have successfully removed the ‘gender’ column from our DataFrame. Notice how we passed the inplace=True parameter to make the changes affect the DataFrame we are working on.
Method 2: Using iloc
The iloc method is another useful technique for removing columns based on index position. iloc is an index-based selection method that allows us to slice rows and columns of a DataFrame using integer indices.
We can also use this method to remove columns as using the index position of the column as shown below:
df.drop(df.columns[[column_index]], axis=1, inplace=True)
column_index: The index position of the column to removeaxis: 0 for rows and 1 for columnsinplace: If True, changes will be made to the DataFrame rather than returning a new one
Here’s an example of removing the ‘name’ column in our DataFrame using the iloc method:
df.drop(df.columns[[0]], axis=1, inplace=True)
print(df)
Output:
age
0 22
1 34
2 19
Method 3: Using del
The del function provides another way of deleting columns in a DataFrame. However, it is different from the first two methods since it modifies the original DataFrame.
Here’s the syntax for using del to remove a column:
del df['column_name']
column_name: The name of the column to remove
Here’s an example of removing the ‘age’ column using the del function:
del df['age']
print(df)
Output:
name gender
0 Alex M
1 Bob M
2 Carry F
Conclusion
In this article, we introduced the Pandas library and showed how to create and view a DataFrame. We also explored three different methods of removing columns from DataFrames: using drop, iloc, and del.
These are useful techniques for selecting and manipulating the data in Pandas DataFrames. By mastering this skill, you will be fully equipped to work on your data analysis project.
Using drop to Remove Columns
The drop method is a versatile way of removing one or more columns from a DataFrame. We already covered the basic syntax of the drop method, but let’s explore some additional features.
Removing Multiple Columns
To remove more than one column, we simply pass a list of column names to the drop method. Here’s an example:
df.drop(['col1', 'col2', 'col3'], axis=1, inplace=True)
This would remove columns ‘col1’, ‘col2’, and ‘col3’ from the DataFrame.
Notice that we set the axis parameter to 1 to indicate that we are removing columns. Also, we used the inplace parameter to modify the original DataFrame.
If we set it to False, a new DataFrame would be returned with the columns removed.
Removing Columns by Name
Sometimes we want to remove columns based on a partial name or a specific name. We can achieve this using the str.contains() method.
Here’s an example:
df = df.loc[:, ~df.columns.str.contains('col')]
This would remove all columns that contain the string ‘col’. The tilde (~) character is used to negate the condition, so we’re keeping columns that don’t contain ‘col’.
This technique is flexible and can be adapted to different scenarios.
Using iloc to Remove Columns
The iloc method is another way of selecting and removing columns based on integer position. We already covered the basic syntax of the iloc method, so let’s explore some advanced features.
Selecting Columns by Position
We can remove columns by specifying their position using iloc. For example, let’s say we want to remove the first and third columns of the DataFrame.
We can do that with the following code:
df.drop(df.columns[[0, 2]], axis=1, inplace=True)
Notice that we used the columns attribute to get a list of the DataFrame’s column names, and then accessed the elements we wanted using integer indexing. This technique can be useful when we know the positions of the columns we want to remove.
Selecting Multiple Columns
To select multiple columns using iloc, we pass a list of column positions to the iloc indexer. For example, let’s say we want to select the first, third, and fifth columns of the DataFrame.
Here’s how we can do that:
df = df.iloc[:, [0, 2, 4]]
Notice that we used the iloc indexer to select all rows of the DataFrame (denoted by a colon), and then accessed the columns we wanted using a list of integer positions. This technique can be useful when we want to select a subset of columns from a larger DataFrame.
Conclusion
In conclusion, we’ve explored some advanced features of the drop and iloc methods for removing columns from a Pandas DataFrame. Specifically, we learned how to remove multiple columns, remove columns by name, select columns by position, and select multiple columns.
These techniques can be useful in a variety of data analysis tasks, and will help you work more effectively with Pandas DataFrames. Keep practicing and experimenting with these methods, and you’ll soon become an expert in manipulating DataFrames in Pandas!
Using del to Remove Columns
The del statement is a simple and powerful way of removing columns from a Pandas DataFrame. It works by directly modifying the DataFrame in place, rather than returning a modified copy, so use it with caution.
As a best practice, it’s often recommended to use the drop() method instead of the del statement, especially if you’re working with a large or complex dataset. But there are times when del can be useful, such as when you need to quickly remove a few columns from a simple DataFrame.
Removing Multiple Columns
To remove multiple columns using del, we simply specify a list of column names. Here’s an example:
del df['col1'], df['col2'], df['col3']
This would remove columns ‘col1’, ‘col2’, and ‘col3’ from the DataFrame.
Notice that we used the comma to separate the statements, which allows us to remove multiple columns in a single line of code. Alternatively, we can use a loop to remove multiple columns from a DataFrame.
Here’s an example:
cols_to_remove = ['col1', 'col2', 'col3']
for col in cols_to_remove:
del df[col]
Notice that we created a list of column names to remove, and then looped over the list and used del to remove each column. This technique is useful if you need to remove columns based on a more complex condition, such as a partial name or a data type.
Removing Columns by Position
To remove columns by position using del, we use the columns attribute to get a list of the DataFrame’s column names, and then access the element we want using integer indexing. Here’s an example:
del df.columns[0], df.columns[2]
This would remove the first and third columns of the DataFrame.
Notice that we used the columns attribute to get a list of the DataFrame’s column names, and then accessed the elements we wanted using integer indexing. Alternatively, we can use a loop to remove columns by position from a DataFrame.
Here’s an example:
cols_to_remove = [0, 2]
for col_idx in sorted(cols_to_remove, reverse=True):
del df[df.columns[col_idx]]
Notice that we created a list of column positions to remove, and then looped over the list in reverse order and used del to remove each column. The reverse order is necessary to avoid problems with index positions changing as we remove columns.
Conclusion
In conclusion, we’ve explored some advanced features of the del statement for removing columns from a Pandas DataFrame. Specifically, we learned how to remove multiple columns and remove columns by position.
These techniques can be useful in a variety of data analysis tasks, but remember to use them with caution, especially if you’re working with a large or complex dataset. Keep practicing and experimenting with these methods, and you’ll soon become an expert in manipulating DataFrames in Pandas!
In this article, we’ve explored various ways to remove columns from a Pandas DataFrame using the drop, iloc, and del methods.
We started by learning how to create and view a DataFrame before delving into techniques for removing one or multiple columns. We also explored how to remove columns by name or position using the different methods.
These techniques are essential skills for any data analyst or scientist who frequently works with tabular data. By following the examples in this article, you’ll be able to efficiently remove columns in large and complex datasets, enabling you to focus on the data that matters the most.
Remember, always use caution when modifying your DataFrame and keep experimenting with different techniques to improve your coding skills.