Reading and writing CSV data in Python - Cheat Sheet & Quick Revision

Recall & Review

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What is a CSV file?

A CSV (Comma-Separated Values) file is a simple text file that stores tabular data. Each line is a row, and columns are separated by commas.

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Which Python module is commonly used to read and write CSV files?

The csv module is used in Python to read from and write to CSV files easily.

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How do you open a CSV file for reading in Python?

Use open('filename.csv', 'r', newline='') to open the file in read mode. The newline='' helps handle newlines correctly.

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What does csv.reader do?

csv.reader reads the CSV file line by line and returns each row as a list of strings.

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How do you write rows to a CSV file in Python?

Use csv.writer to create a writer object, then call writer.writerow(row) for each row you want to write.

Which Python code correctly opens a CSV file for writing?

A open('data.csv', 'r')

B open('data.csv', 'a')

C open('data.csv', 'w', newline='')

D open('data.csv')

To write to a CSV file, open it with mode 'w' and use newline='' to avoid extra blank lines.

What does the csv.reader return for each row?

A A list of strings

B A dictionary

C A string

D An integer

csv.reader returns each row as a list of strings representing the columns.

Which delimiter is used by default in CSV files?

A Semicolon (;)

B Comma (,)

C Tab (\t)

D Space ( )

CSV stands for Comma-Separated Values, so the default delimiter is a comma.

How do you write multiple rows at once using csv.writer?

A writer.writerows(list_of_rows)

B writer.writerow(list_of_rows)

C writer.write(list_of_rows)

D writer.write_rows(list_of_rows)

writer.writerows() writes multiple rows from a list of lists.

Why use newline='' when opening CSV files?

A To read files faster

B To add extra blank lines

C To encrypt the file

D To prevent extra blank lines on Windows

Using newline='' prevents Python from adding extra blank lines when writing CSV files on Windows.

Explain how to read data from a CSV file in Python step-by-step.

Think about opening the file, reading rows, and what each row looks like.

Describe how to write data to a CSV file in Python.

Focus on opening the file, creating the writer, writing rows, and closing the file.