Writing records to a CSV file

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Quick Questions

Shade in the A or B circle for each question.

1. Which line joins the fields of a record list called record into one CSV line?

A line = ','.join(record)

B line = record.join(',')

2. record = ['Ava', 16, 'Red']. What happens when you run ','.join(record)?

A 'Ava,16,Red'

B TypeError, because 16 is not a string

3. Which record is safe to pass to ','.join()?

A ['Ava', str(16), 'Red']

B ['Ava', 16, 'Red']

4. You write a line to a CSV file with file.write(line). What is missing so each record sits on its own row?

A file.write(line + '\n')

B file.write(line + ',')

5. Which approach writes a header row to a new CSV file correctly?

A file.write(['name', 'age'])

B file.write(','.join(['name', 'age']) + '\n')

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1','.join(record)		Afile.write('name,mark\n')
2str(record[2])		BJoins the string fields of a record into one comma-separated line ready to write to a CSV file
3Write a header row first so the CSV file has column names, then the data lines		CNo newline is added, so every record ends up on the same line. Add + '\n' after the joined text.
4Append a new record to the end of an existing CSV file without erasing the old lines		DConverts a number field to a string so it can be joined into a CSV line
5line = ','.join(['Ava', 88])		Eopen('marks.csv', 'a')
6file.write(','.join(record))		FThe number 88 is not a string, so join() causes a TypeError. Use str(88) first.

Definitions

','.join(record)

Fill in the Blanks

Complete each line of code by filling in the missing parts.

line = ','.____(record)

line = ','.join([name, ___(score)])

row = [name, str(score)] f._____(','.join(row) + '\n')

with open('scores.csv', '_') as f: f.write(','.join(row) + '\n')

header = ','.join(['Name', 'Score']) f.write(______ + '\n')

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A f = open("pupils.csv", "r")

B row = ["Ava", "16", "Red"]

C line = ",".join(row)

D f.write(line + "\n")

E f.close()

Question 2

A row = ["Liam", 15, "Blue"]

B line = ",".join(row)

C with open("p.csv", "a") as f:

D f.write(line + "\n")

Question 3

A with open("s.csv", "w") as f:

B f.write("item price\n")

C row = ["Pen", str(1.5)]

D line = ",".join(row)

E f.write(line + "\n")

Question 4

A row = ["Zoe", str(88), "A"]

B line = row.join(",")

C f = open("marks.csv", "a")

D f.write(line + "\n")

E f.close()

Question 5

A f = open("kids.csv", "w")

B r = ["Al", "7"]

C f.write(",".join(r) + "/n")

D f.close()

Answer Key

Writing records to a CSV file

Section A: Quick Questions

A — line = ','.join(record)

B — TypeError, because 16 is not a string

A — ['Ava', str(16), 'Red']

A — file.write(line + '\n')

B — file.write(','.join(['name', 'age']) + '\n')

Section B: Match the Pairs

','.join(record) → Joins the string fields of a record into one comma-separated line ready to write to a CSV file

str(record[2]) → Converts a number field to a string so it can be joined into a CSV line

Write a header row first so the CSV file has column names, then the data lines → file.write('name,mark\n')

Append a new record to the end of an existing CSV file without erasing the old lines → open('marks.csv', 'a')

line = ','.join(['Ava', 88]) → The number 88 is not a string, so join() causes a TypeError. Use str(88) first.

file.write(','.join(record)) → No newline is added, so every record ends up on the same line. Add + '\n' after the joined text.

Section C: Definitions

','.join(record) — Joins a record's fields, which must all be strings, into one comma-separated line. Use str() on numbers first, then write the line plus a newline to the CSV file.

Section D: Fill in the Blanks

line = ','.join(record)

line = ','.join([name, str(score)])

row = [name, str(score)]
f.write(','.join(row) + '\n')

with open('scores.csv', 'a') as f:
    f.write(','.join(row) + '\n')

header = ','.join(['Name', 'Score'])
f.write(header + '\n')

Section E: Spot the Error

A — Mode "r" opens the file for reading only, so f.write() would fail. To save records the file must be opened in write mode: open("pupils.csv", "w").

A — 15 is an integer, and join() only accepts strings, so line 2 would crash with a TypeError. Convert the number first with str(15).

B — The header row must use commas to separate the column names, like the data rows. It should be f.write("item,price\n").

B — join() is a string method, and lists have no join method. The separator string comes first and the record goes inside the brackets: ",".join(row).

C — The newline character is \n with a backslash. "/n" would write the literal characters /n into the file instead of ending the line. It should be "\n".