Python CSV: Read and Write CSV files

1) Create & Write a Simple CSV

Create a CSV file data.csv with rows:

name,age
Alice,20
Bob,22

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2) Read Entire CSV

Read data.csv from #1 and print each row.

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3) Read CSV as List

Read data.csv and store all rows in a list, then print that list.

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4) Write CSV with User Input

Ask the user to enter 3 names and ages and write them into users.csv.

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5) Read Only First Column

Read users.csv and print only the name column.

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6) Read Only Second Column

Read users.csv and print only the age column.

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7) Append a Row

Open data.csv and append:

Charlie,25

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8) Count Rows

Read a CSV and print how many data rows it has (ignore header).

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9) Write CSV with Headers

Create and write a CSV products.csv with headers:

id,product,price

and 3 product rows.

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10) Read with DictReader

Use csv.DictReader to read products.csv and print each row as a dictionary.

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11) Write with DictWriter

Ask the user for product data and write to products2.csv using csv.DictWriter and headers id,product,price.

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12) Increase Prices

Read products.csv, increase all prices by 10%, and write results to a new CSV file.

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13) Filter Rows

Read products.csv and print only rows where price > 50.

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14) Save Filtered Rows

Read products.csv and write only rows with price > 50 to expensive.csv.

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15) Convert CSV to List of Dicts

Read a CSV and convert it to a list of dictionaries, then print that list.

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16) Sum Numeric Column

Read products.csv and compute the total of the price column.

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17) Average Price

Read products.csv and print the average price of all items.

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18) CSV to Text File

Read products.csv and write each row as a line in a text file like:

id: 1, product: Pen, price: 10

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19) Check for Header

Write code that reads any CSV and prints:

Has header

if the first row contains any strings (not only numbers).

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20) Merge Two CSV Files

Given two CSVs with the same headers, combine them into one CSV.

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🧠 Concepts Practiced

Topic	What You Learn
Writing CSV	csv.writer, DictWriter
Reading CSV	csv.reader, DictReader
Headers	Use of first row as header
Filtering	Reading and deciding rows to keep
Aggregation	Summing/averaging numeric columns
Conversion	To lists, dictionaries, text format

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📝 Starter Code Snippets

Writing a CSV

import csv

with open("data.csv","w",newline="") as f:
    writer = csv.writer(f)
    writer.writerow(["name","age"])
    writer.writerow(["Alice","20"])
    writer.writerow(["Bob","22"])

Reading a CSV

import csv

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

Using DictReader

import csv

with open("products.csv") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(row["product"], row["price"])

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