Summary

In this lab, we introduced several major important topics in Python. Let’s quickly review them.

Booleans in Python

• True
• False
• bool() procedure to convert values
  • If the input is the value False, the value 0, the value None, or anything with 0 length, including the empty string, it will return False.
  • Otherwise, for all other values it will return True.

Boolean Operators

• and
• or
• not

Boolean Comparators

• == equal
• != not equal
• < less than
• <= less than or equal to
• > greater than
• >= greater than or equal to

Comparators and Strings

Strings are compared using lexicographic order

Boolean Order of Operations

1. Math operators (following their order of operations)
2. Boolean comparators
3. not
4. and
5. or

Conditional Statements

• if statement

if <boolean expression>:
    <block of statements>

• if-else statement

if <boolean expression>:
    <block of statements 1>
else:
    <block of statements 2>

Testing

• Branch Coverage - all possible branches are executed at least once
• Path Coverage - all possible paths through branches are executed at least once
• Edge Cases - values that are near the point where Boolean expressions go from False to True

Mutually Exclusive

Conditional statements are mutually exclusive when only one of the many branches will be executed for any possible input.

Chained Conditionals

if condition_1:
    print("1")
else
    if condition_2:
        print("2")
    else:
        if condition_3:
            print("3")
        else:
            print("4")

is equivalent to:

if condition_1:
    print("1")
elif condition_2:
    print("2")
elif condition_3:
    print("3")
else:
    print("4")

Nested Conditionals

if condition_1:
    if condition_2:
        print("1 and 2")
    elif condition_3:
        print("1 and 3")
    else:
        print("1 and not 2 or 3")
elif condition_4:
    if condition_2:
        print("4 and 2")
    elif condition_3:
        print("4 and 3")
    else:
        print("4 and not 2 or 3")
else:
    print("neither 1 nor 4")

Variable Scope

Variable scope refers to what parts of the code a particular variable is accessible in. Python uses function scope, which means that a variable defined anywhere in a function is available below that definition in any part of the same function.

Other languages use block scope, where variables are only available within the block where they are defined.