Should you teach 'expressions' in a Python course?

During a Python beginners course I usually briefly explain what an expression is.

It is not essential to know the term ’expression’, but I find it very helpful when explaining some essential concepts, such as what happens when you create a new variable.

Of course not everyone wants to know in detail how things work. Some people only care about the rules, the syntax. So I keep it quite short.

I usually cover expressions something like this:

If you’re new to Python or to programming, you don’t really need to know what an ’expression’ is. But I will be using the term a few times during the course, so let’s quickly go over it.

An expression is anything which returns a value. You can save this value for later use using a variable. Or you can use right it now, for instance by printing it.

An expression can be a simple variable

age = 10
print(age)    # Expression: age

Or a calculation

age = 10
print(age + 1)   # Expression: age + 1

Or the result of calling a function

name = 'Amara'
print(len(name))    # Expresion: len(name)

Or a combination of any of these

name = 'Amara'
print(len(name) + 10)    # Expresion: len(name) + 10

Often, when the object already exists, that object is returned.

# Create a new object - a float with value 1.53
# and 'bind' it to the name 'amount'
amount = 1.53

# the expression '= age' does not create a new object 
# but returns a reference to the existing one, 
# created in the previous step
amount_copy = amount

# Both age and age_copy now refer to the same object

Whilst other expressions create a new object.

total = 5 * 1.73
name = 'Jonathan'
number_of_characters = len(name)

All of these create a new object, and ‘bind’ it to a new name (total, name and number_of_characters)