1. CSC115 Introduction to Computer Programming
Zhen Jiang
Dept. of Computer Science
West Chester University
West Chester, PA 19383

2. Table of Contents Review of Basic I/O Condition and Decision Making
Format/Syntax and Execution
Boolean Expression
Development
Multiple selection
Nested if
Code alignment and end of block
== and is

3. Review Output Number String Combination (by using + and str) Input
Type
Conversion (float and int)
Processing
Feel it in the test

4. Condition and Decision Making
A deterministic output by a given input
Big-or-small?
Random.randint(1,6), store and not show
Guess 123 small or 456 big
Won or lost?

5. No
Yes
Condition
Action 1
Action 2
Action 3

6. Boolean Expression Action 1 If controlled Action 2 else controlled
Yes No
Boolean
Expression
Action 1
If controlled
Action 2
else controlled
Action 3
11/9/2018

7. Syntax and Execution If block if condition : action 1 (statements 1)
else :
action 2 (statements 2)
# a blank line to separate
action 3 (statement 3)

8. Boolean Expression Simple condition Complex condition Format
<Value> <relational operators> <Value>
Number value relational operators
==, !=, <, >, <=, >=
!!! Number one error: “a=2” instead of “a==2”
String value relational operators
left for later discussion
Complex condition
And, or, not
Truth table

9. Truth table Precedence orderF C2
C1 and C2
C1 or C2
not C1
Truth table
Precedence order

10. Relational operators have lower precedence than math operators.
(7 - 1) * > 7* 5
6 * > 35
> 35
33 > 35
False
Relational operators cannot be chained (unlike math operators)
2 <= x <= 10
error!
11/9/2018

11. Development Process Identify two exclusive options
Implement each handling in different action parts
Identify the situation (values) for option selection
Make a condition so that all the situation value for option part 1 will lead to this condition true.
Verify all the situation value for option part 2 will lead to this condition false, otherwise, revise the above condition!

13. Multiple selection
Nested if (chained condition)
Example: letter grade

14. Nested if for multiple section problem
If then
case 1
Else
if then
case 2
else …
end if
End if

16. Conditional and alternative execution
if condition :
action 1 (statements 1)
# no else!
action 3 (statement 3)

18. Are they different, how much?
x = int(input("enter Int: ")) y = 0 if x > 3 : y = if x < 10 : y = 2 else : y =3 print(y)
x = int(input("enter Int: ")) y = 0 if x > 3 : y = 1 if x < 10 : y = 2 else : y =3 print(y)

19. Try 0, 4, 11 and see the results! 3 4 2 11 1 2 4 11 3

20. Indeed x = int(input("enter Int: ")) y = 0 if x > 3 : y = 1
x = int(input("enter Int: ")) y = 0 if x > 3 : y = if x < 10 : y = 2 else : y =3 print(y)
x = int(input("enter Int: ")) y = 0 if x > 3 : y = 1
if x < 10 : y = 2 else : y =3 print(y)

21. My point One line in wrong place Structural procedure
Could cause the program 99.99% different
Location/alignment maters!
Blank line is useful
Structural procedure
Ask yourself where (the next program segment line) the computer execution goes
Before that, check if you can find the “if” for each “else”

22. Try enter “3” and “3”:
a = int(input("first string: ")) b = int(input ("second string: ")) if a == b : print("same content") else: print("not the same content") if a is b : print ("same string") else: print ("not the same string")

23. Try this program and enter “3” and “3”.
a = input("first string: ") b = input("second string: ") if a == b : print("same content") else: print("not the same content") if a is b : print ("same string") else: print ("not the same string")

24. Same code, try “a3” and “a3”.
a = input("first string: ") b = input("second string: ") if a == b : print("same content") else: print("not the same content") if a is b : print ("same string") else: print ("not the same string")