# Conditionals

Programming basics[1]

Programs generally run sequentially, starting from the first instruction and then moving to the next instruction, in a step-by-step process. A computer will read line one, execute line one, and then go to line two, for example. It is common to include conditional statements to decide if a program should "do something else" if a specific condition is true or false.

A conditional statement evaluates an expression and executes instructions depending on the outcome of the evaluation. Conditionals depend on operators to evaluate if an expression is true or false. A condition and selection are not the same thing. A condition asks a question. A selection processes the answer.

With gratitude to and permission from Stephen Hughes (Coe College) and Philip East (University of Northern Iowa)[2], The list below is an example of types of conditional questions. You should start thinking about conditions in plain english before you start thinking about operators.

• Match
• Threshold
• Range
• One-of
• Not-match
• Not one of
• All of
• Some of
• Eligible

## Conditional code sample

```# this file helps us to understand conditionals in Python.
# what do you think the output will be when you execute these instructions?

a = 5
b = "bar"

if a == 5:
print("Yes, the variable a has been assigned to the value 5.")
else:
print("No, the variable a has not been assigned to the value 5.")

# what do you think the output will be when you execute these instructions?

a = 5
b = "bar"

if b == "foo":
print("yes, the variable b has been assigned the value foo")
else:
print("no, the variable b has been assigned to some other value than foo.")
```

## Multiple conditionals code sample

```# this file helps us to understand multiple conditionals in Python.
# what do you think the output will be when you execute these instructions?

a = 5
b = "bar"

if (a == 5 and b == "bar"):
print("both conditions are true.")
else:
print("one or both of the conditions are false")

# what do you think the output will be when you execute these instructions?

a = 5
b = "bar"

if (a == 5 or b == "bar"):
print("both conditions are true.")
else:
print("one or both of the conditions are false")
```

## Conditional code sample with lists

```# this file helps us to understand conditionals in Python.
# what do you think the output will be when you execute these instructions?

myList = ["foo","bar","baz"]

if "foo" in myList:
print("Foo is in the list")
else:
print("Foo is not in list")

# what do you think the output will be when you execute these instructions?

myList = ["foo","bar","baz"]

if "bar" not in myList:
print("bar is in the list")
else:
print("bar is not in list")
```