More Practice Programs

11 · Celsius to Fahrenheit

Problem: ask for a temperature in Celsius and display it in Fahrenheit. The formula is F = (C × 9/5) + 32.

c = float(input('Temperature in Celsius: '))

f = c * 9 / 5 + 32

print(c, 'Celsius is', f, 'Fahrenheit')

Temperature in Celsius: 37
37.0 Celsius is 98.6 Fahrenheit

No brackets are needed round c * 9 / 5 because * and / already run before +. Put them in anyway if it helps you read it — (c * 9 / 5) + 32 is the same program.

c = float(input('Temperature in Celsius: '))

f = c * 9 / 5 + 32

print(c, 'Celsius is', f, 'Fahrenheit')

22 · Simple interest

Problem: ask for the principal, the rate of interest and the time in years. Print the simple interest and the total amount to be paid back. The formula is SI = (P × R × T) / 100.

p = float(input('Principal amount: '))
r = float(input('Rate of interest per year: '))
t = float(input('Time in years: '))

si = (p * r * t) / 100
amount = p + si

print('Simple interest =', si)
print('Amount to be paid =', amount)

Principal amount: 10000
Rate of interest per year: 7.5
Time in years: 3
Simple interest = 2250.0
Amount to be paid = 12250.0

p = float(input('Principal amount: '))
r = float(input('Rate of interest per year: '))
t = float(input('Time in years: '))

si = (p * r * t) / 100
amount = p + si

print('Simple interest =', si)
print('Amount to be paid =', amount)

33 · Area and perimeter of a rectangle

Problem: ask for the length and breadth of a rectangle. Print its area and its perimeter. Area = l × b, perimeter = 2 × (l + b).

l = float(input('Length: '))
b = float(input('Breadth: '))

area = l * b
perimeter = 2 * (l + b)

print('Area =', area)
print('Perimeter =', perimeter)

Length: 12
Breadth: 5
Area = 60.0
Perimeter = 34.0

The brackets in the perimeter are doing real work. Without them, 2 * l + b doubles only the length — 29 instead of 34, with no complaint from Python.

l = float(input('Length: '))
b = float(input('Breadth: '))

area = l * b
perimeter = 2 * (l + b)

print('Area =', area)
print('Perimeter =', perimeter)

44 · Swapping two values

Problem: ask for two numbers and print them with their values exchanged. This one is a classic because the obvious answer is wrong.

x = 10
y = 20

x = y      # x is now 20 — and the old 10 is gone forever
y = x      # so this copies 20 back into y

print('x =', x, 'and y =', y)

x = 20 and y = 20

Both boxes end up holding 20. The moment x = y runs, the original 10 has nowhere left to live. The fix is a third box to hold it while you move things:

x = float(input('First number: '))
y = float(input('Second number: '))

temp = x     # keep x safe
x = y
y = temp

print('After swapping: x =', x, 'and y =', y)

First number: 10
Second number: 20
After swapping: x = 20.0 and y = 10.0

x = float(input('First number: '))
y = float(input('Second number: '))

temp = x
x = y
y = temp

print('After swapping: x =', x, 'and y =', y)

55 · Seconds into hours, minutes and seconds

Problem: ask for a number of seconds and print it as hours, minutes and seconds. 3725 seconds should come out as 1 hour, 2 minutes and 5 seconds.

Same tool as the height program: // for how many whole units fit, % for what is left over.

total = int(input('Number of seconds: '))

hours = total // 3600          # 3600 seconds in an hour
remaining = total % 3600       # what is left after the hours

minutes = remaining // 60      # 60 seconds in a minute
seconds = remaining % 60       # and what is left after those

print(hours, 'hour(s),', minutes, 'minute(s),', seconds, 'second(s)')

Number of seconds: 3725
1 hour(s), 2 minute(s), 5 second(s)

total = int(input('Number of seconds: '))

hours = total // 3600
remaining = total % 3600

minutes = remaining // 60
seconds = remaining % 60

print(hours, 'hour(s),', minutes, 'minute(s),', seconds, 'second(s)')

6Now write these on your own

No solutions for these. Each one is a rearrangement of something above, so if you can do the five programs on this page you can do all six of these:

Use the box below as your notebook — it is a full Python file, so write any of them here and press Run.

# write your program here

7Recap