Type checking in Python
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Which check confirms that the string age is made up of digits only?
2. What does "abc".isdigit() return?
3. Which code is a type check using try/except?
4. What happens when int("hello") runs without try/except?
5. Which input would "25".isdigit() accept as a valid number entry?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1age.isdigit() | AReturns True only if the string age contains digits only, so it passes as a whole number | |
| 2int(value) | Bif not score.isdigit(): print("Enter a number") | |
| 3Reject text where a number is needed by testing the string before using it | CThe except block has no try before it, so int(value) is not protected and the code is a syntax error. | |
| 4Use try/except to catch input that cannot be converted to an integer | Disdigit() is a string method, so it must be called on the string as age.isdigit(), not as a stand-alone function. | |
| 5if isdigit(age): | ETries to convert text to a whole number and raises ValueError if it cannot | |
| 6n = int(value) except ValueError: | Ftry: n = int(value) except ValueError: print("Not a number") |
C
Definitions
isdigit()
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
age = input("Age: ")
if age._______():
print("Age accepted")
2.
try:
age = ___(input("Age: "))
except ValueError:
3.
try:
score = int(entry)
except __________:
4.
if ___ age.isdigit():
print("Numbers only!")
5.
try:
num = int(value)
______ ValueError:
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
age = input("Age: ")
B
if age.isdigit():
C
print("Valid number")
D
else
E
print("Not a number")
Question 2
A
try;
B
qty = int(input("Qty: "))
C
except ValueError:
D
print("Not a number")
Question 3
A
value = int(input("Enter score: "))
B
if value.isdigit():
C
print("Accepted")
D
else:
E
print("Rejected")
Question 4
A
text = input("Quantity: ")
B
if text.isdigit():
C
qty = int(text)
D
print("Total:", text * 2)
E
else:
F
print("Digits only")
Question 5
A
text = input("Age: ")
B
if text.isdigit:
C
print("Valid")
D
else:
E
print("Invalid")
Answer Key
Type checking in Python
Section A: Quick Questions
Q1
B — age.isdigit()
Q2
B — False
Q3
A — try:
n = int(value)
except ValueError:
print("Not a number")
Q4
A — The program crashes with a ValueError
Q5
A — "25" (returns True)
Section B: Match the Pairs
Q1
age.isdigit() → Returns True only if the string age contains digits only, so it passes as a whole number
Q2
int(value) → Tries to convert text to a whole number and raises ValueError if it cannot
Q3
Reject text where a number is needed by testing the string before using it → if not score.isdigit():
print("Enter a number")
Q4
Use try/except to catch input that cannot be converted to an integer → try:
n = int(value)
except ValueError:
print("Not a number")
Q5
if isdigit(age): → isdigit() is a string method, so it must be called on the string as age.isdigit(), not as a stand-alone function.
Q6
n = int(value)
except ValueError: → The except block has no try before it, so int(value) is not protected and the code is a syntax error.
Section C: Definitions
Q1
isdigit() — A type check method: returns True if a string holds only digits, so text can be rejected where a number is needed. The alternative is to put int(value) inside try/except.Section D: Fill in the Blanks
Q1
age = input("Age: ")
if age.isdigit():
print("Age accepted")Q2
try:
age = int(input("Age: "))
except ValueError:Q3
try:
score = int(entry)
except ValueError:Q4
if not age.isdigit():
print("Numbers only!")Q5
try:
num = int(value)
except ValueError:Section E: Spot the Error
Q1
D — The else keyword must be followed by a colon. The line should be else:
Q2
A — A try block starts with a colon, not a semicolon. The line should be try:
Q3
A — isdigit() only works on strings. Converting the input to an int first would crash on the next line. It should be value = input("Enter score: ") so the text can be checked first.
Q4
D — text is still a string, so text * 2 repeats the text instead of doubling the number. It should use the converted number: qty * 2.
Q5
B — isdigit is a method and needs brackets to run. Without them the condition is always true, so text is never rejected. It should be if text.isdigit():