Python - Variables

Question 1

What is a variable?

Answer 1

Think of variables as labels that you can assign to values. You can also say that a variable references a certain value.

Question 2

What does it mean to ‘bind’ a variable?

Answer 2

Binding a variable means to set a name to hold a reference to some object. Object deletion may automatically follow, by garbage collection, when no more references to an object exist.

A del statement consists of the keyword del, followed by one or more target references separated by commas (,).

Question 3

What does it mean to ‘unbind’ a variable?

Answer 3

Unbinding a variable means to reset the variable name so it no longer holds a reference.

Question 4

What does the ‘del’ statement do?

Answer 4

The ‘del’ statement unbinds a variable reference, although doing so is rare.

Question 5

What does it mean to ‘rebind’ a variable?

Answer 5

Binding a reference that was already bound is also known as rebinding.

Question 6

What are some naming conventions for a variable?

Answer 6

Cannot use a keyword.

Question 7

Name some keywords.

Answer 7

and
break
elif
from
is
pass
with
as
class
else
global
lambda
raise
yield
assert
continue
except
if
nonlocal
return
False
async
def
finally
import
not
try
None
await
del
for
in
or
while
True

Question 8

What is a ‘global’ variable?

Answer 8

A global variable is an attribute of a module object.

Question 9

What is a ‘local’ variable?

Answer 9

A local variable lives in a function’s local namespace .

Question 10

What does ‘namespace’ or ‘scope’ mean?

Answer 10

The function body, make up the function’s local namespace, also known as its local scope.

Question 11

What does ‘assignment’ mean for variables in Python?

Answer 11

Assignment is when an value or object binds to a variable name (i.e. identifier)

Example: target = expression

Question 12

What are the two types of assignments for variables in Python?

Answer 12

The two types of assignments for variables in Python are Plain Assignment and Augmented Assignment.

Question 13

What is a ‘plain assignment’ for Python variables?

Answer 13

Plain assignment to a variable (e.g., name = value) is how you create a new variable or rebind an existing variable to a new value.

Question 14

What is an ‘augmented assignment’ for Python variables?

Answer 14

Augmented assignment can
* rebind a variable,
* ask an object to rebind one of its existing attributes or items, or
* request the target object to modify itself.

Augmented assignment (e.g., name += value) cannot, per se, create new references.

Question 16

What is a ‘Plain Assignment’ for variables in Python?

Answer 16

Plain assignment to a variable (e.g., name = value) is how you create a new variable or rebind an existing variable to a new value.

target = expression

Question 17

What is the ‘unpacking assignment’ for variables in Python?

Answer 17

The unpacking assignment in Python binds each reference in the target to the corresponding item in the Right Hand Side:

a, b, c = x # x must be an iterable with the exact amount of values
a, b = b, a # swapping value without a 3rd variable
first, *middle, last = x # the starred identifier gets the left over value(s)
first, middle, last = x[0], x[1:-1], x[-1] # same as previous

Question 18

What is an ‘Augmented Assignment’ for variables in Python?

Answer 18

An augmented assignment (sometimes called an in-place assignment) differs from a plain assignment in that, instead of an equals sign (=) between the target and the expression, it uses an augmented operator, which is a binary operator followed by =. The augmented operators are +=, -=, *=, /=, //=, %=, **=, |=,&raquo_space;=, «=, &=, ^=, and @=.

Augmented assignment does not support multiple targets.