# Import the library
import pandas as pd
# Create a DataFrame
df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
# Read a CSV file
df = pd.read_csv('file.csv')
# Select a single column
df['A']
# Select multiple columns
df[['A', 'B']]
# Select rows by their position
df[0:2]
# Select rows by their labels
df.loc[labels]
# Select rows by condition
df[df['A'] > 2]
# Apply a function to a column
df['A'].apply(np.sqrt)
# Group by a column
df.groupby('A').mean()
# Save a DataFrame to a CSV file
df.to_csv('file.csv')
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