Python If-else Problems

Python If-else Problems

Assign grades from marks

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Python Practice › If-Else Programs › Program 3

Assign grades from marks

EasyIf-Else Programs · 3 of 64

Write a Python program to assign a grade from total marks: below 40 Fail, 40-49 C, 50-59 B, 60-69 A, 70-79 A+, 80-89 A++, 90-100 Excellent, anything else Invalid.

Input
35, 47, 68, 85, 100, 105
Output
35 -> Fail
47 -> C
68 -> A
85 -> A++
100 -> Excellent
105 -> Invalid marks

Approach

  1. Reject values outside 0-100 first.
  2. Then test the ranges from the highest down, so each elif only needs a lower bound.

Solution

Python
def grade(marks):    if marks < 0 or marks > 100:        return "Invalid marks"    elif marks >= 90:        return "Excellent"    elif marks >= 80:        return "A++"    elif marks >= 70:        return "A+"    elif marks >= 60:        return "A"    elif marks >= 50:        return "B"    elif marks >= 40:        return "C"    else:        return "Fail" for m in [35, 47, 68, 85, 100, 105]:    print(m, "->", grade(m))
Output
35 -> Fail
47 -> C
68 -> A
85 -> A++
100 -> Excellent
105 -> Invalid marks

Line by line

Lines 2-3

Invalid input is handled first so the other branches can assume 0 to 100.

Lines 4-15

Because Python stops at the first true branch, testing from the top down means marks >= 80 only runs for marks below 90.

Lines 16-17

Anything below 40 falls through to else.

Note

The original task listed “marks > 40: Fail”, which would fail almost everyone. It should be marks below 40.

Learn the concept

New to this topic? Read the lesson, then come back.

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Numbers from 1 to 30 divisible by 3

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Python Practice › If-Else Programs › Program 2

Numbers from 1 to 30 divisible by 3

EasyIf-Else Programs · 2 of 64

Write a Python program to print all the numbers from 1 to 30 that are divisible by 3.

Output
3 6 9 12 15 18 21 24 27 30

Approach

  1. Loop from 1 to 30 and print a number only when n % 3 == 0.

Solution 1: loop with if

Python
for n in range(1, 31):    if n % 3 == 0:        print(n, end=" ")print()
Output
3 6 9 12 15 18 21 24 27 30

Line by line

Line 1

range(1, 31) stops before 31, so 30 is included.

Line 3

end=" " keeps the numbers on one line.

Line 4

An empty print() ends the line.

Solution 2: range with a step

Python
print(list(range(3, 31, 3)))
Output
[3, 6, 9, 12, 15, 18, 21, 24, 27, 30]

Line by line

Line 1

Starting at 3 with a step of 3 produces only multiples of 3, so no if is needed.

Learn the concept

New to this topic? Read the lesson, then come back.

More if-else programs

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← All 64 If-Else Programs

Check if a number is divisible by 3

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Python Practice › If-Else Programs › Program 1

Check if a number is divisible by 3

EasyIf-Else Programs · 1 of 64

Write a Python program to check whether a given number is divisible by 3.

Input
21, 22
Output
21 is divisible by 3
22 is not divisible by 3

Approach

  1. A number is divisible by 3 when the remainder n % 3 is 0.

Solution

Python
for n in [21, 22]:    if n % 3 == 0:        print(n, "is divisible by 3")    else:        print(n, "is not divisible by 3")
Output
21 is divisible by 3
22 is not divisible by 3

Line by line

Line 1

The loop tests two sample numbers so both branches run.

Line 2

% gives the remainder; a remainder of 0 means an exact division.

Lines 4-5

else handles every other case.

Learn the concept

New to this topic? Read the lesson, then come back.

More if-else programs

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Python If-Else Programs with Solutions

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Python Practice › If-Else Programs

Python If-Else Programs with Solutions

64 programs59 easy5 medium0 hard

64 if-else programs that practise decisions in Python: comparisons, elif chains, nested conditions and combining tests with and / or. Each solution tests several inputs so you can see every branch run.

Before you start

Read the If…Else and Match Case lesson first if the topic is new to you.

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