DataFrames

DataFrames are one of the core data structures in Pandas and are essential for working with structured data. Think of a DataFrame as a table similar to a spreadsheet or SQL table, but designed for more flexible and powerful data operations. Each column in a DataFrame can be of a different data type, making it a versatile tool for data manipulation.

Creating DataFrames

To start working with DataFrames, you can create them using various methods. One of the simplest ways is by using a Python dictionary. Each key in the dictionary represents a column name, and the corresponding value is a list of column values.

import pandas as pd

data = {
    'Name': ['Alice', 'Bob', 'Charlie'],
    'Age': [25, 30, 35],
    'Occupation': ['Engineer', 'Doctor', 'Artist']
}

df = pd.DataFrame(data)
print(df)

This will output:

      Name  Age Occupation
0    Alice   25   Engineer
1      Bob   30     Doctor
2  Charlie   35     Artist

You can also create a DataFrame from a list of dictionaries, where each dictionary represents a row of data.

data = [
    {'Name': 'Alice', 'Age': 25, 'Occupation': 'Engineer'},
    {'Name': 'Bob', 'Age': 30, 'Occupation': 'Doctor'},
    {'Name': 'Charlie', 'Age': 35, 'Occupation': 'Artist'}
]

df = pd.DataFrame(data)

Loading DataFrames from Files

In practical scenarios, data is often stored in files. Pandas provides functions to easily load data from CSV, Excel, SQL databases, and more. Here's how to load a CSV file:

df = pd.read_csv('data.csv')

This command reads the content of data.csv into a DataFrame called df. Pandas automatically infers the data types of each column, making it straightforward to start analyzing the data immediately.

Exploring DataFrames

Once you have a DataFrame, you can look into its structure and content. Use the head() method to view the first few rows:

print(df.head())

The info() method provides a concise summary of the DataFrame:

df.info()

This will display the number of entries, column names, data types, and memory usage, helping you understand the dataset at a glance.

Selecting Data

Selecting specific data from a DataFrame is a common task. You can select columns by passing their names as strings:

ages = df['Age']

To select multiple columns, pass a list of column names:

subset = df[['Name', 'Occupation']]

Rows can be selected using the loc[] and iloc[] methods. Use loc[] for label-based indexing and iloc[] for positional indexing:

# Select rows by label
row = df.loc[0]

# Select rows by position
row = df.iloc[0]

Modifying DataFrames

You can easily add, modify, or delete columns in a DataFrame. To add a new column, simply assign the data to a new column name:

df['Salary'] = [70000, 80000, 75000]

To modify an existing column, assign new values to it:

df['Age'] = df['Age'] + 1

Deleting a column is just as straightforward:

df.drop('Salary', axis=1, inplace=True)

Summary Statistics

DataFrames provide several methods to quickly perform summary statistics:

print(df.describe())

The describe() method returns a summary of statistics for numerical columns, such as mean, median, and standard deviation. For more specific operations, methods like mean(), sum(), and count() are available:

average_age = df['Age'].mean()
total_entries = df['Age'].count()

Conclusion

DataFrames are powerful yet intuitive structures that simplify the process of data analysis. By mastering DataFrames, you gain a versatile tool for handling data in a variety of forms, helping you tackle more complex data science tasks and analyses with confidence.