Testing letters with isalpha() and isupper()

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. A Caesar loop reads the character ' ' (a space). What does ' '.isalpha() return?

A False, so the space is left unchanged

B True, so the space is shifted

2. Which line correctly tests whether the character ch is a letter?

A if ch.isalpha():

B if isalpha(ch) == ch:

3. What does '!'.isalpha() return in Python?

A False

B True

4. Why does a Caesar encryption loop check ch.isalpha() before shifting?

A So the loop shifts every character, including spaces

B So only letters are shifted and spaces and punctuation stay the same

5. Which character makes 'G'.isupper() return True?

A G is a letter, so isupper() always returns True for any letter

B G is a capital letter, so it returns True

Match the Pairs

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

Left column		Right column
1ch.isalpha()		AReturns True if the letter ch is a capital letter, so the loop knows whether to shift from 'A' or from 'a'
2ch.isupper()		Belse: result += ch
3Only shift a character if it is a letter, so spaces and punctuation stay unchanged		Cif ch.isalpha():
4Leave a character unchanged when it is not a letter by adding it to the result as it is		Disalpha() is a string method, so it is written after the character with a dot. It must be ch.isalpha().
5if ch.isalpha:		EThe brackets are missing, so Python checks the method itself and not its result. It must be ch.isalpha().
6if isalpha(ch):		FReturns True if the character ch is a letter, and False for spaces, digits and punctuation

Definitions

ch.isalpha()

Fill in the Blanks

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

for ch in message: if ch._______(): result += ch

for ch in message: __ ch.isalpha(): shift = 3

ch = 'q' print(ch._______()) # prints False

if ___ ch.isalpha(): result += ch continue

base = 65 if ch.isupper() else __

Spot the Error

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

Question 1

A for ch in message

B if ch.isalpha():

C result += ch

Question 2

A for ch in text:

B if ch.isalpha:

C print(ch, 'letter')

Question 3

A result = ''

B for ch of text:

C if ch.isalpha():

D result += ch

Question 4

A word = 'Hello'

B if word[0].isUpper():

C print('Capital start')

Question 5

A result = ''

B for ch in text:

C if ch.isalpha():

D result = shift(ch)

E else:

F result += ch

Answer Key

Testing letters with isalpha() and isupper()

Section A: Quick Questions

A — False, so the space is left unchanged

A — if ch.isalpha():

A — False

B — So only letters are shifted and spaces and punctuation stay the same

B — G is a capital letter, so it returns True

Section B: Match the Pairs

ch.isalpha() → Returns True if the character ch is a letter, and False for spaces, digits and punctuation

ch.isupper() → Returns True if the letter ch is a capital letter, so the loop knows whether to shift from 'A' or from 'a'

Only shift a character if it is a letter, so spaces and punctuation stay unchanged → if ch.isalpha():

Leave a character unchanged when it is not a letter by adding it to the result as it is → else: result += ch

if ch.isalpha: → The brackets are missing, so Python checks the method itself and not its result. It must be ch.isalpha().

if isalpha(ch): → isalpha() is a string method, so it is written after the character with a dot. It must be ch.isalpha().

Section C: Definitions

ch.isalpha() — Returns True if the character ch is a letter, so a Caesar loop can shift letters and leave spaces and punctuation unchanged. ch.isupper() checks for capitals.

Section D: Fill in the Blanks

for ch in message:
    if ch.isalpha():
        result += ch

for ch in message:
    if ch.isalpha():
        shift = 3

ch = 'q'
print(ch.isupper())
# prints False

if not ch.isalpha():
    result += ch
    continue

base = 65 if ch.isupper() else 97

Section E: Spot the Error

A — A for loop header must end with a colon. It should be: for ch in message:

B — isalpha is a method, so it needs brackets to run. Without them Python just checks that the method exists, so the test always passes. It should be: if ch.isalpha():

B — Python loops use the keyword in, not of. It should be: for ch in text:

B — Python method names are case-sensitive. The method is isupper() with all lowercase letters, not isUpper().

D — Using = replaces result each time, so only the last character is kept. It should be result += shift(ch) to add to the message.