Get first n records of a Pandas DataFrame

Working with large datasets in Pandas can often be a daunting task, especially when it comes to retrieving the first few records of a dataset. In this article, we will explore the various ways to get the first n records of a Pandas DataFrame.

Installation and Setup

We must make sure that Pandas is installed on our system before moving further with the implementation ?

pip install pandas

Once installed, we can create a DataFrame or load a CSV and then retrieve the first N records.

Methods to Get First n Records

A Pandas DataFrame's first n entries can be obtained in several ways. Here are the most commonly used techniques ?

• df.head(n) Retrieve the first n rows of the DataFrame. The default value of n is 5 if not specified.

• df.iloc[:n] Get the first n rows of the DataFrame using integer-based indexing.

• df.loc[:n-1] Fetch the first n rows of the DataFrame using label-based indexing.

• df[:n] This is the slice operator in Python which gets the first n rows using implicit slicing.

Example Implementation

Let's create a sample DataFrame and demonstrate each method to retrieve the first 5 records ?

import pandas as pd

# Create a sample DataFrame
df = pd.DataFrame({
    'Name': ['John', 'Mary', 'Peter', 'Jane', 'Mike', 'Alex', 'Sandy', 'Ben', 'Alice', 'Cooper'],
    'Age': [25, 32, 18, 45, 27, 39, 32, 19, 29, 18],
    'Country': ['USA', 'Canada', 'UK', 'Australia', 'USA', 'Canada', 'UK', 'Australia', 'USA', 'Canada']
})

print("Original DataFrame:")
print(df)

Original DataFrame:
     Name  Age    Country
0    John   25        USA
1    Mary   32     Canada
2   Peter   18         UK
3    Jane   45  Australia
4    Mike   27        USA
5    Alex   39     Canada
6   Sandy   32         UK
7     Ben   19  Australia
8   Alice   29        USA
9  Cooper   18     Canada

Using head() Method

The head() method is the most common and recommended way to get the first n records ?

import pandas as pd

df = pd.DataFrame({
    'Name': ['John', 'Mary', 'Peter', 'Jane', 'Mike', 'Alex', 'Sandy', 'Ben'],
    'Age': [25, 32, 18, 45, 27, 39, 32, 19],
    'Country': ['USA', 'Canada', 'UK', 'Australia', 'USA', 'Canada', 'UK', 'Australia']
})

# Get first 5 records using head()
print("First 5 records using head():")
print(df.head(5))

First 5 records using head():
    Name  Age    Country
0   John   25        USA
1   Mary   32     Canada
2  Peter   18         UK
3   Jane   45  Australia
4   Mike   27        USA

Using iloc Indexing

The iloc method uses integer-based indexing to select rows ?

import pandas as pd

df = pd.DataFrame({
    'Name': ['John', 'Mary', 'Peter', 'Jane', 'Mike', 'Alex', 'Sandy', 'Ben'],
    'Age': [25, 32, 18, 45, 27, 39, 32, 19],
    'Country': ['USA', 'Canada', 'UK', 'Australia', 'USA', 'Canada', 'UK', 'Australia']
})

# Get first 3 records using iloc
print("First 3 records using iloc:")
print(df.iloc[:3])

First 3 records using iloc:
    Name  Age Country
0   John   25     USA
1   Mary   32  Canada
2  Peter   18      UK

Using Slice Operator

The slice operator provides a simple way to get the first n records ?

import pandas as pd

df = pd.DataFrame({
    'Name': ['John', 'Mary', 'Peter', 'Jane', 'Mike', 'Alex', 'Sandy', 'Ben'],
    'Age': [25, 32, 18, 45, 27, 39, 32, 19],
    'Country': ['USA', 'Canada', 'UK', 'Australia', 'USA', 'Canada', 'UK', 'Australia']
})

# Get first 4 records using slice operator
print("First 4 records using slice operator:")
print(df[:4])

First 4 records using slice operator:
    Name  Age    Country
0   John   25        USA
1   Mary   32     Canada
2  Peter   18         UK
3   Jane   45  Australia

Comparison of Methods

Common Use Cases

Getting the first n records has several practical applications ?

• Exploratory data analysis Quick way to understand the structure and content of the data.

• Data sampling Extract a subset of data for testing and training in machine learning.

• Data visualization Plot a subset of data for better performance and clarity.

• Data validation Check data quality and format before processing large datasets.

Conclusion

The head() method is the most commonly used and recommended approach for getting the first n records of a DataFrame. Use iloc for integer-based indexing needs and the slice operator for quick, Pythonic selection. All methods provide fast performance for data exploration and analysis.