Length check with len()

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Date:

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Quick Questions

Shade in the A or B circle for each question.

1. Which condition checks that a PIN is exactly 4 characters long?

A pin == 4

B len(pin) == 4

2. A password must have a minimum length of 8 characters. Which check accepts it?

A len(password) >= 8

B len(password) <= 8

3. A username can be at most 12 characters. Which check accepts it?

A len(username) >= 12

B len(username) <= 12

4. A length check tests the...

A number of characters in the input

B meaning of the input

5. Which line is a correct length check in Python?

A if len(code) == 6:

B if len(code) = 6:

Match the Pairs

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

Left column		Right column
1len(pin) == 4		AChecks that the password is at least 8 characters long
2len(password) >= 8		BUsing > means an 8-character password is rejected. For a minimum of 8 it should be len(password) >= 8.
3Accept a username only if it has no more than 12 characters (maximum length)		Cif len(pin) != 4:
4Reject a PIN that is not exactly 4 characters long		Dif len(username) <= 12:
5if pin == 4:		EChecks that the PIN is exactly 4 characters long
6if len(password) > 8:		FThe PIN text is compared directly with the number 4. It should compare its length: len(pin) == 4.

Definitions

len(pin) == 4

Fill in the Blanks

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

if ___(pin) == 4:

if len(pin) __ 4:

if len(password) __ 8:

valid = len(username) __ 12

pin = input("Enter 4-digit PIN: ") if len(pin) == _: print("PIN accepted")

Spot the Error

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

Question 1

A if len(pin) = 4:

B print('PIN accepted')

C else:

D print('PIN rejected')

Question 2

A pin = input('PIN: ')

B valid = False

C if pin == 4:

D valid = True

E print(valid)

Question 3

A pw = input('Password: ')

B if len(pw) <= 8:

C print('Strong enough')

D else:

E print('Too short')

Question 4

A name = input('Username: ')

B limit = 12

C if len[name] <= limit:

D print('OK')

E else:

F print('Too long')

Question 5

A pin = input('Enter PIN: ')

B while len(pin) != 4:

C print('Must be 4 digits')

D pin == input('Try again: ')

E print('PIN saved')

Answer Key

Length check with len()

Section A: Quick Questions

B — len(pin) == 4

A — len(password) >= 8

B — len(username) <= 12

A — number of characters in the input

A — if len(code) == 6:

Section B: Match the Pairs

len(pin) == 4 → Checks that the PIN is exactly 4 characters long

len(password) >= 8 → Checks that the password is at least 8 characters long

Accept a username only if it has no more than 12 characters (maximum length) → if len(username) <= 12:

Reject a PIN that is not exactly 4 characters long → if len(pin) != 4:

if pin == 4: → The PIN text is compared directly with the number 4. It should compare its length: len(pin) == 4.

if len(password) > 8: → Using > means an 8-character password is rejected. For a minimum of 8 it should be len(password) >= 8.

Section C: Definitions

len(pin) == 4 — A length check compares len() of the text with a required length or limit, such as exactly 4 characters for a PIN, to accept or reject the input.

Section D: Fill in the Blanks

if len(pin) == 4:

if len(password) >= 8:

valid = len(username) <= 12

pin = input("Enter 4-digit PIN: ")
if len(pin) == 4:
    print("PIN accepted")

Section E: Spot the Error

A — A single = assigns a value, so it cannot compare the length. A length check needs the comparison operator ==, as in if len(pin) == 4:.

C — pin is text, so it is never equal to the number 4. The check must compare the length of the text: if len(pin) == 4:.

B — A minimum length check must accept passwords that are 8 or more characters. <= accepts only short ones, so it should be >=.

C — len is a function, so it is called with round brackets, not square brackets. It should be len(name).

D — A double == compares values instead of storing the new input, so pin never changes and a wrong PIN loops forever. It should be a single = to assign: pin = input('Try again: ').