Check a prime number

Python Practice › Basic Programs › Program 28

Check a prime number

MediumBasic Programs · 28 of 40

Write a Python program to check whether a number is prime (greater than 1 and divisible only by 1 and itself).

Input

29, 33, 1, 97

Output

29 True
33 False
1 False
97 True

Approach

Numbers below 2 are not prime.
Try dividing by every number from 2 up to the square root; any exact division means not prime.

Solution

Python

def is_prime(n):    if n < 2:        return False    for d in range(2, int(n ** 0.5) + 1):        if n % d == 0:            return False    return True for n in [29, 33, 1, 97]:    print(n, is_prime(n))

Output

29 True
33 False
1 False
97 True

Line by line

Lines 2-3

0, 1 and negative numbers are not prime.

Line 4

Checking up to √n is enough: if n had a factor larger than √n, it would also have one smaller than √n.

Lines 5-6

Return False as soon as a divisor is found.

Line 7

No divisor was found, so the number is prime.

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#29EasyCheck a leap year #30MediumCheck for an anagram #31EasyGenerate random numbers #32EasyRandom string of a given length

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Compound interest

Python Practice › Basic Programs › Program 27

Compound interest

EasyBasic Programs · 27 of 40

Write a Python program to calculate compound interest. Amount = P × (1 + R/100)ᵀ and interest = amount − P.

Input

P = 10000, R = 8, T = 5 (compounded yearly)

Output

Amount: 14693.28
Compound interest: 4693.28

Approach

Compute the final amount with the formula.
Subtract the principal to get the interest.

Solution

Python

principal = 10000rate = 8years = 5 amount = principal * (1 + rate / 100) ** yearsinterest = amount - principalprint("Amount:", round(amount, 2))print("Compound interest:", round(interest, 2))

Output

Amount: 14693.28
Compound interest: 4693.28

Line by line

Line 5

(1 + rate / 100) is the growth factor per year; ** years applies it for every year.

Lines 7-8

round(..., 2) shows rupees and paise.

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#28MediumCheck a prime number #29EasyCheck a leap year #30MediumCheck for an anagram #31EasyGenerate random numbers

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Check a palindrome number

Python Practice › Basic Programs › Program 26

Check a palindrome number

EasyBasic Programs · 26 of 40

Write a Python program to check whether a number is a palindrome (reads the same backwards, like 12321).

Input

12321, 12345

Output

12321 is a palindrome
12345 is not a palindrome

Approach

Reverse the digits and compare with the original.

Solution

Python

def is_palindrome(n):    text = str(n)    return text == text[::-1] for n in [12321, 12345]:    print(n, "is a palindrome" if is_palindrome(n) else "is not a palindrome")

Output

12321 is a palindrome
12345 is not a palindrome

Line by line

Lines 2-3

Comparing the string with its reverse gives True or False directly.

Line 6

A conditional expression chooses the message.

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#27EasyCompound interest #28MediumCheck a prime number #29EasyCheck a leap year #30MediumCheck for an anagram

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Fibonacci series up to 50

Python Practice › Basic Programs › Program 25

Fibonacci series up to 50

EasyBasic Programs · 25 of 40

Write a Python program to print the Fibonacci series between 0 and 50. Each number is the sum of the two before it.

Output

[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

Approach

Start with a = 0 and b = 1.
Print a, then move forward with a, b = b, a + b until a passes 50.

Solution

Python

a, b = 0, 1series = []while a <= 50:    series.append(a)    a, b = b, a + bprint(series)

Output

[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

Line by line

Line 1

The series starts with 0 and 1.

Line 3

The loop stops as soon as the next number would be above 50.

Line 5

Both variables update at once: the new a is the old b, and the new b is the sum of the old pair.

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#26EasyCheck a palindrome number #27EasyCompound interest #28MediumCheck a prime number #29EasyCheck a leap year

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Reverse a number

Python Practice › Basic Programs › Program 24

Reverse a number

EasyBasic Programs · 24 of 40

Write a Python program to reverse the digits of a number.

Input

Output

Approach

Take the last digit with % 10 and remove it with // 10.
Build the reversed number digit by digit.

Solution 1: arithmetic

Python

n = 12345reversed_n = 0while n > 0:    digit = n % 10    reversed_n = reversed_n * 10 + digit    n //= 10print(reversed_n)

Output

Line by line

Line 4

n % 10 is the last digit (5 first).

Line 5

Shifting the result one place left (* 10) and adding the digit appends it.

Line 6

//= 10 removes the last digit; the loop ends when n reaches 0.

Solution 2: string slicing

Python

n = 12345print(int(str(n)[::-1]))

Output

Line by line

Line 2

Convert to a string, reverse it with [::-1] and convert back to int.

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#25EasyFibonacci series up to 50 #26EasyCheck a palindrome number #27EasyCompound interest #28MediumCheck a prime number

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Factorial of a number

Python Practice › Basic Programs › Program 23

Factorial of a number

EasyBasic Programs · 23 of 40

Write a Python program to find the factorial of a number. n! = 1 × 2 × … × n, and 0! = 1.

Input

n = 6

Output

6! = 720

Approach

Start with 1 and multiply by every number from 2 to n.

Solution 1: loop

Python

n = 6factorial = 1for i in range(2, n + 1):    factorial *= iprint(f"{n}! = {factorial}")

Output

6! = 720

Line by line

Line 2

Start at 1, the identity for multiplication (and the value of 0!).

Line 3

range(2, n + 1) gives 2, 3, 4, 5, 6; the end value is excluded, so add 1.

Line 4

*= multiplies the running result by each number.

Solution 2: math.factorial

Python

import mathprint(math.factorial(6), math.factorial(0))

Output

720 1

Line by line

Line 2

The standard library already has an efficient factorial function.

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#24EasyReverse a number #25EasyFibonacci series up to 50 #26EasyCheck a palindrome number #27EasyCompound interest

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Days between two dates

Python Practice › Basic Programs › Program 22

Days between two dates

EasyBasic Programs · 22 of 40

Write a Python program to calculate the number of days between two dates.

Input

(2023, 1, 5) and (2023, 1, 22)

Output

17 days

Approach

Create two date objects.
Subtract them to get a timedelta and read its .days.

Solution

Python

from datetime import date start = date(2023, 1, 5)end = date(2023, 1, 22)gap = end - startprint(gap.days, "days")

Output

17 days

Line by line

Line 5

Subtracting dates gives a timedelta object.

Line 6

.days is the whole number of days between them.

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#23EasyFactorial of a number #24EasyReverse a number #25EasyFibonacci series up to 50 #26EasyCheck a palindrome number

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Print the current date in a format

Python Practice › Basic Programs › Program 21

Print the current date in a format

EasyBasic Programs · 21 of 40

Write a Python program to print the current date in the format “2023 Jan 05” (year, short month name, day) using the datetime module.

Output

2026 Nov 02

Approach

Get today’s date with date.today().
Format it with strftime("%Y %b %d").

Solution

Python

from datetime import date today = date.today()print(today.strftime("%Y %b %d"))

Output

2026 Nov 02

Line by line

Line 3

date.today() reads the date from your computer’s clock.

Line 4

%Y is the 4-digit year, %b the short month name and %d the 2-digit day.

Note

The output shows the date on which this page was built. Press Try it and Run to see today’s date.

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#22EasyDays between two dates #23EasyFactorial of a number #24EasyReverse a number #25EasyFibonacci series up to 50

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Simple interest

Python Practice › Basic Programs › Program 20

Simple interest

EasyBasic Programs · 20 of 40

Write a Python program to calculate simple interest. Simple interest = P × R × T / 100, where P is the principal, R the yearly rate in percent and T the time in years.

Input

P = 10000, R = 6.5, T = 3

Output

Simple interest: 1950.0
Total amount: 11950.0

Approach

Apply the formula.
Add the interest to the principal for the total amount.

Solution

Python

principal = 10000rate = 6.5years = 3 interest = principal * rate * years / 100amount = principal + interestprint("Simple interest:", interest)print("Total amount:", amount)

Output

Simple interest: 1950.0
Total amount: 11950.0

Line by line

Line 5

Dividing by 100 converts the percentage rate into a fraction.

Line 6

The amount repaid is the principal plus the interest.

Note

The original version of this exercise listed the formula as P + (P/r)*t, which is not the simple interest formula. The correct formula is P × R × T / 100.

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#21EasyPrint the current date in a format #22EasyDays between two dates #23EasyFactorial of a number #24EasyReverse a number

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Check an Armstrong number

Python Practice › Basic Programs › Program 19

Check an Armstrong number

MediumBasic Programs · 19 of 40

Write a Python program to check whether a number is an Armstrong number: the sum of its digits, each raised to the power of the number of digits, equals the number (153 = 1³ + 5³ + 3³).

Input

153, 370, 123, 9474

Output

153 True
370 True
123 False
9474 True

Approach

Count the digits.
Raise each digit to that power and add them up.
Compare the sum with the original number.

Solution

Python

def is_armstrong(n):    digits = str(n)    power = len(digits)    total = sum(int(d) ** power for d in digits)    return total == n for n in [153, 370, 123, 9474]:    print(n, is_armstrong(n))

Output

153 True
370 True
123 False
9474 True

Line by line

Line 2

Turning the number into a string makes it easy to loop over its digits.

Line 3

The power is the number of digits: 3 for 153, 4 for 9474.

Line 4

The generator expression converts each digit back to int, raises it to power and sum() adds them.

Line 5

The function returns True only when the sum equals the number.

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#20EasySimple interest #21EasyPrint the current date in a format #22EasyDays between two dates #23EasyFactorial of a number

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