A control statement is a statement that determines the control flow of a set of instructions.
Sequence control is an implicit form of control in which instructions are executed in the order that they are written.
Selection control is provided by a control statement that selectively executes instructions.
Iterative control is provided by an iterative control statement that repeatedly executes instructions.
One way of producing Boolean values is by comparing
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num = 10 # Assignment Operator
num == 12 # Comparison operator
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We know that we can compare number for sure, but Python also let's us compare String values based on their character encoding.
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10 == 20
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print(type('2'))
print('2' < '9')
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if "Aliya" > "Alican":
print("Aliya is the best!")
else:
print("No, Aliya is not the best!")
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'Hello' == "hello"
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'Hello' > 'Zebra'
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Another way to get Boolean values is by checking if the membership of given value is valid or not:
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'Dr.' in 'Dr. Madison'
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10 not in (10, 20, 30)
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Boolean (logical) operators , denoted by and, or, and not in Python. It is basically logic,
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p = False
r = True
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p and r
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p or r
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not (r and (not p))
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The boolean operators will give us a more complex comparison statements which eventually will lead us to better control structures.
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num = 15
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(1 <= num <= 10)
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# Above is equals to
1 <= num and num <= 10
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(10 < 0) and (10 > 2)
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not(True) and False
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not(True and False)
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name = 'Ann'
name in ('Thomas', 'MaryAnn', 'Thomas')
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type(('MarryAnn'))
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A selection control statement is a control statement providing selective execution of instructions.
An if statement is a selection control statement based on the value of a given Boolean expression.
Syntax:
if condition:
statements
else:
statements
You don't have to include else part.
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if 10 < 0:
print("Yes")
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grade = 66
if grade >= 70:
print('Passing Grade')
else:
print('Failing Grade')
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grade = 100
if grade == 100:
print('Perfect Score!')
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credits = 45
if credits >= 90:
print('Senior')
else:
if credits >= 60:
print('Junior')
else:
if credits >= 30:
print('Sophomore')
else:
if credits >= 1:
print('Freshman')
else:
print('* No Earned Credits *')
However there is a better way to do this using an additional keyword: elif
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credits = 45
if credits >= 90:
print('Senior')
elif credits >= 60:
print('Junior')
elif credits >= 30:
print('Sophomore')
elif credits >= 1:
print('Freshman')
else:
print('* No Earned Credits *')
Write a small program that prints the day of the specific month of a year. The output will look like this:
Test 1:
This program will determine the number of days in a given month
Enter the month (1-12): 14
*Invalid Value Entered -14*
Test 2:
This program will determine the number of days in a given month
Enter the month (1-12): 2
Please enter the year (e.g., 2010): 2000
There are 29 days in the month
Use if and elif statements
Hint1:
The days of the month are fixed regardless of the year, except February.
Check for 2.
Hint2:
If the year is divisible by 4 but is also divisible by 100, then it is not a leap year— unless, it is also divisible by 400, then it is.
Hint3:
(year % 4 == 0) and (not (year % 100 == 0) or (year % 400 == 0))
An iterative control statement is a control statement providing the repeated execution of a set of instructions.
Because of the repeated execution, iterative control structures are commonly referred to as “loops” and that's how I am going to name them :)
A while statement is an iterative control statement that repeatedly executes a set of statements based on a provided Boolean expression (condition).
Syntax:
while condition:
statement
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# Initial variables
total = 0
i = 1
n = int(input('Enter value: '))
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while i <= n:
total += i # total = total + i
i += 1
print(total)
As long as the condition of a while statement is true, the statements within the loop are (re)executed.
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import time
n = 10
tot = 0
i = 1
while i <= n:
tot = tot + i
i = i + 1
print(tot)
time.sleep(2)
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n = 100
tot = 0
while True:
tot = tot + n
n = n - 1
if n == 0:
break
print(tot)
An infinite loop is an iterative control structure that never terminates (or eventually terminates with a system error). Usually programming errors
let's inspect the following snippet:
# add up first n integers
tot = 0
current = 1
n = int(input('Enter value: ')
while current <= n:
tot = tot + current
If your program got stuck in infinite loop you can use special keyboard interruption such as ctrl+C-
Write a small program that displays a random value between 1 and 99 cents, and ask user to enter a set of coins that sums exactly to the amount shown.You should use while loop, if statement, Boolean Flag, random number generator The output will look like this:
The purpose of this exercise is to enter a number of coin values that add up to a displayed target value.
Enter coins values as 1-penny, 5-nickel, 10-dime, and 25-quarter.
Hit return/enter after the last entered coin value.
------------------
Enter coins that add up to 63 cents, one per line.
Enter first coin: 25
Enter next coin: 25
Enter next coin: 10
Enter next coin:
Sorry - you only entered 60 cents.
Try again (y/n)?: y
Enter coins that add up to 21 cents, one per line.
Enter first coin: 11
Invalid entry
Enter next coin: 10
Enter next coin: 10
Enter next coin: 5
Sorry - total amount exceeds 21 cents.
Try again (y/n)?: y
Enter coins that add up to 83 cents, one per line.
Enter first coin: 25
Enter next coin: 25
Enter next coin: 25
Enter next coin: 5
Enter next coin: 1
Enter next coin: 1
Enter next coin: 1
Enter next coin:
Correct!
Try again (y/n)?: n
Thanks for playing ... goodbye
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