Python Programming · Week 5
Hyeongmin Lee · SeoulTech, Dept. of Electronic Engineering
The same steps as last week.
This video is all typing. Pause whenever you need to catch up.
On paper: what comes out? Then type it at the prompt. An empty line runs the loop.
>>>for i in range(1, 10, 3):
... print(i)
...
>>>x = 1
>>>while x < 50:
... x = x * 2
...
>>>x
>>>total = 0
>>>for i in range(1, 6):
... if i == 3:
... continue
... total += i
...
>>>total
In your week05 folder: the nine lines from the theory video.
n = int(input("How many scores? "))
total = 0
for i in range(1, n + 1):
score = int(input(f"Score {i}: "))
while score < 0 or score > 100:
print("A score is from 0 to 100.")
score = int(input(f"Score {i}: "))
total += score
print(f"Average: {total / n}")How many scores? 3
Score 1: 95
Score 2: 150
A score is from 0 to 100.
Score 2: 72
Score 3: 88
Average: 85.0
run again0 and 100 are scores too
How many scores? 2
Score 1: 0
Score 2: 100
Average: 50.0
A new file, total.py: the sum of 1 to 5 from the theory video.
1total = 0
2for i in range(1, 6):
3 total = total + i
4print(total)
what VARIABLES shows, in each iteration
the trace table from the theory video · live, one step at a time
In avg.py, on purpose. After each one, undo it: ⌘Z (Windows: Ctrl+Z).
avg.py, line 7
delete the line that asks again · type 3, 95, 150
A score is from 0 to 100. (again and again)
stop it with Ctrl+C
avg.py, line 3
change n + 1 to n · type 3, 95, 72
Average: 55.666666666666664
an off-by-one error: Score 3 is never asked
avg.py, line 9
indent the last line · type 3, 95, 72, 88
Average: 31.666666666666668 … after every score
inside the loop now
an infinite loop: Ctrl+C · two silent wrong answers: the worst case
Four new lines in avg.py.
n = int(input("How many scores? "))
total = 0
highest = 0
for i in range(1, n + 1):
score = int(input(f"Score {i}: "))
while score < 0 or score > 100:
print("A score is from 0 to 100.")
score = int(input(f"Score {i}: "))
total += score
if score > highest:
highest = score
print(f"Average: {total / n}")
print(f"Highest: {highest}")
How many scores? 3
Score 1: 95
Score 2: 150
A score is from 0 to 100.
Score 2: 72
Score 3: 88
Average: 85.0
Highest: 95
the maximum: start low, replace when bigger
0 is low enough: every score is from 0 to 100
Ask for an integer, 0 or more. Print the sum of its digits.
n % 10: the remainder, the last digit · n // 10: the quotient, n without its last digit
on the screen
Number: 2026
Digit sum: 10
Number: 99999
Digit sum: 45
the code
n = int(input("Number: "))
total = 0
while n > 0:
total += n % 10
n = n // 10
print(f"Digit sum: {total}")Ask for a number of rows. Row 1 shows 1, row 2 shows 1 2, row 3 shows 1 2 3, and so on.
each row is a loop of its own: a loop inside a loop
on the screen
Rows: 4
1
1 2
1 2 3
1 2 3 4
the code
n = int(input("Rows: "))
for row in range(1, n + 1):
for k in range(1, row + 1):
print(k, end=" ")
print()Ask for an integer, 2 or more. Print whether it is prime: divisible only by 1 and by itself.
count the divisors from 1 to n · a prime has exactly 2
on the screen
Number: 7
7 is prime
Number: 91
91 is not prime
the code
n = int(input("Number: "))
count = 0
for d in range(1, n + 1):
if n % d == 0:
count += 1
if count == 2:
print(f"{n} is prime")
else:
print(f"{n} is not prime")Ask for a number from 2 to 9. Anything else: From 2 to 9, please. and ask again, until it is. Then print its times table, from n x 1 up to n x 9.
on the screen · one run
Number (2 to 9): 12
From 2 to 9, please.
Number (2 to 9): 7
7 x 1 = 7
7 x 2 = 14
7 x 3 = 21
7 x 4 = 28
7 x 5 = 35
7 x 6 = 42
7 x 7 = 49
7 x 8 = 56
7 x 9 = 63
the values after the prompts are typed · the prompt words are up to you
examples · typed values in order
typed
prints
7
7 x 1 = 7 … 7 x 9 = 63
12, 3
From 2 to 9, please. then 3 x 1 = 3 … 3 x 9 = 27
1, 0, 9
the message twice, then 9 x 1 = 9 … 9 x 9 = 81
Ask for n (1 or more). Print the first n Fibonacci numbers on one line. The first two are 1 and 1. Each next number is the sum of the two before it. Hint: keep the last two numbers in two variables.
on the screen · one run
How many? 10
1 1 2 3 5 8 13 21 34 55
the values after the prompts are typed · the prompt words are up to you
examples · typed values in order
typed
prints
1
1
2
1 1
10
1 1 2 3 5 8 13 21 34 55
15
1 1 2 3 5 8 13 21 34 55 89 144 233 377 610
Ask for n (1 or more). Print the n-th prime number: 2, 3, 5, 7, 11, 13, … Hint: example 3 checks one number. Check 2, 3, 4, … in turn, count the primes, and stop when the count reaches n.
on the screen · one run
n: 10
Prime #10: 29
the values after the prompts are typed · the prompt words are up to you
examples · typed values in order
typed
prints
1
Prime #1: 2
5
Prime #5: 11
10
Prime #10: 29
100
Prime #100: 541
Next steps
Before class. Everything you need is on e-Class.
See you in class.