Reading CSV files in Python

Assume you have a CSV file named data.csv with this content:

name,age,city
Alice,20,Toronto
Bob,22,Montreal
Charlie,25,Vancouver

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1) Read Entire CSV

Read data.csv and print each row as a list.

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2) Skip Header

Read data.csv and print only data rows (skip the header).

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3) Print First Column

Read data.csv and print only the name column.

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4) Print Second Column

Read data.csv and print only the age column.

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5) Print Third Column

Read data.csv and print only the city column.

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6) Count Rows

Read data.csv and print how many data rows (excluding header) it has.

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7) Print Ages as Integers

Read ages from data.csv, convert to int, and print.

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8) List of Names

Read data.csv and save all names into a list, then print the list.

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9) Names Above Certain Age

Read data.csv and print names of people older than 21.

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10) Print in Formatted Lines

Display each row like:

Alice (20) lives in Toronto

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11) Read Using DictReader

Read data.csv using csv.DictReader and print each row as a dictionary.

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12) Print Names Using DictReader

Use csv.DictReader and print only the name value from each row.

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13) Print Age + City Together

Use DictReader and combine fields:

20 — Toronto

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14) Sum of Ages

Read all ages from the CSV and print their total.

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15) Average Age

Read ages and print the average age.

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16) Unique Cities

Read the file and print a list of unique cities (no duplicates).

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17) Search Name

Ask user for a name and print the corresponding row if found.

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18) Save Ages to List

Extract the age column into a list of integers and print it.

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19) Count by City

Read data.csv and count how many people are from each city.

Expected output example:

Toronto: 1
Montreal: 1
Vancouver: 1

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20) Print All Rows Reverse Order

Read all rows (excluding header) and print them in reverse order.

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🔎 Useful Code Snippets

Basic Reader

import csv

with open("data.csv") as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)

DictReader

import csv

with open("data.csv") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(row)

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📌 Notes for Students

🟢 Use csv.reader when you want each row as a list. 🟡 Use csv.DictReader when you want each row as a dictionary with headers. 🔵 Always skip the header when doing data-only tasks (unless using DictReader).

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canvil: 333f6c7d-6876-4f7e-b6ad-1bdb2233f5c1