Conditional statements and operators

Introduction to Python for Developers

George Boorman

Curriculum Manager, DataCamp

Booleans

# Boolean variable
the_truth = True
print(the_truth)

True

Used to make comparisons

Operators

Comparison operators
- Symbols or combinations of symbols
- Used to compare things
- Similar to symbols for calculations such as *, +, - etc.
Check if two things are equal
- ==

Checking for equality

# Compare if 2 is equal to 3
2 == 3

False

# Check that 2 is not equal to 3
2 != 3

True

Common use-case: checking login details

Numeric comparison operators

# Is 5 less than 7?
5 < 7

True

# Is 5 less than or equal to 7?
5 <= 7

True

# Is 5 greater than 7?
5 > 7

False

# Is 5 greater or equal to 7?
5 >= 7

False

Other comparisons

# Is James greater than Brian
"James" > "Brian"

True

Strings are evaluated in alphabetical order

Conditional statements

If True perform a task
- otherwise, do nothing
if > condition is met > perform action

# Target units sold and actual units sold
sales_target = 350
units_sold = 355


# Compare sales
if units_sold >= sales_target

Conditional statements

# Target units sold and actual units sold
sales_target = 350
units_sold = 355


# Compare sales
if units_sold >= sales_target:

Conditional statements

# Target units sold and actual units sold
sales_target = 350
units_sold = 355


# Compare sales
if units_sold >= sales_target:

    print("Target achieved")

'Target achieved'

Indentation

# Target units sold and actual units sold
sales_target = 350
units_sold = 355


# Compare sales
if units_sold >= sales_target:

print("Target achieved") # This line is not indented

    print("Target achieved")
    ^
IndentationError: expected an indented block

Elif statement

# Target units sold and actual units sold
sales_target = 350
units_sold = 325

# Compare sales
if units_sold >= sales_target:

    print("Target achieved")

# Check if we were close to the target
elif units_sold >= 320:
    print("Target almost achieved")

Can use as many elif keywords as we like!

Else statement

# Compare sales
if units_sold >= sales_target:
    print("Target achieved")

# Check if we were close to the target
elif units_sold >= 320:
    print("Target almost achieved")

# Otherwise...
else:
    print("Target not achieved")

Comparison operators cheat sheet

Operator	Function
`==`	Equal to
`!=`	Not equal to
`>`	More than
`>=`	More than or equal to
`<`	Less than
`<=`	Less than or equal to

Keyword	Function	Use
`if`	If condition is met	First in the workflow
`elif`	Else check if condition is met	After `if`
`else`	Else perform this action	After `elif`

Let's practice!

Introduction to Python for Developers