Removing Duplicate Rows in a DataFrame Based on a Condition

What will you learn?

In this tutorial, you will master the art of eliminating duplicate rows from a pandas DataFrame by setting specific conditions. This skill is crucial for maintaining data integrity and improving analysis accuracy.

Introduction to the Problem and Solution

Duplicate rows can skew data analysis results and lead to inaccurate insights. By leveraging Python’s pandas library, we can efficiently filter out redundant information based on defined criteria. This process not only streamlines data cleaning but also enhances the quality of our analytical outcomes.


# Importing necessary library
import pandas as pd

# Creating a sample DataFrame
data = {'A': [1, 1, 2, 2], 'B': ['x', 'x', 'y', 'z']}
df = pd.DataFrame(data)

# Dropping duplicates based on column 'A'
filtered_df = df.drop_duplicates(subset='A')

# Displaying the filtered DataFrame

# Copyright PHD


To remove duplicate rows from a DataFrame based on a condition in Python: 1. Import the pandas library. 2. Create a sample DataFrame with duplicate rows. 3. Utilize the drop_duplicates() method with the subset parameter to specify the column for identifying duplicates. 4. Store the resulting DataFrame without duplicates in filtered_df.

    How does drop_duplicates() function work in pandas?

    The drop_duplicates() function eliminates duplicate rows from a DataFrame.

    Can we specify multiple columns as subset in drop_duplicates()?

    Yes, you can pass a list of column names to the subset parameter to consider multiple columns for identifying duplicates.

    Will drop_duplicates() modify the original DataFrame?

    By default, it returns a new DataFrame without altering the original unless specified using additional parameters.

    What happens if there are no duplicated rows?

    If no duplicated rows exist in the specified subset/columns, it returns the original DataFrame unchanged.

    Does drop_duplicates() consider all columns by default?

    By default, all columns are considered when searching for duplicates unless specified using the subset parameter.

    Can we choose which occurrence of duplicated row gets retained?

    Yes, you can use parameters like keep=’first’ or keep=’last’ within drop_duplicates() to control which occurrence is retained.

    Does drop_duplicates() compare values strictly or loosely while removing duplicates?

    By default, it compares values strictly (case-sensitive strings or exact numerical matches). Custom comparison functions can be used if needed.

    Is there an inplace parameter for drop_duplicates() function?

    Yes, setting inplace=True within .drop_duplicate() applies changes directly to your original dataframe.

    Are NaN values considered equal during removal of duplicates?

    NaN values are not considered equal unless explicitly mentioned using parameters like na_equal=True inside .drop_duplicate().


    In conclusion… The detailed explanation provided above guides you through efficiently removing duplicate rows from a pandas dataframe based on specific conditions. This ensures cleaner datasets for more accurate and reliable analysis results.

    Leave a Comment