Selecting Columns

Definition: You pick a column by name with square brackets. One column returns a Series; a list of columns returns a smaller DataFrame.

Example 1 — a single column

import pandas as pd
df = pd.DataFrame({
  "name": ["Sam", "Alex", "Jo"],
  "age":  [25, 30, 22],
  "city": ["London", "Paris", "Rome"]
})
print(df["name"])        # a Series

Example 2 — multiple columns

Use a list of names (note the double brackets):

import pandas as pd
df = pd.DataFrame({
  "name": ["Sam", "Alex", "Jo"],
  "age":  [25, 30, 22],
  "city": ["London", "Paris", "Rome"]
})
print(df[["name", "city"]])   # a DataFrame

Working with a selected column

import pandas as pd
df = pd.DataFrame({"age": [25, 30, 22]})
print(df["age"].mean())   # average age
print(df["age"].max())    # oldest

💡 Tip: remember the rule — single brackets df["age"] give a Series, double brackets df[["age"]] give a DataFrame.