Assigning an object to a variable binds (associates) that variable’s name to the object. As you’ve seen, you can then use the variable in your code to access the object’s value:

In [4]: x = 7

In [5]: x + 10
Out[5]: 17

In [6]: x
Out[6]: 7

After snippet [4]’s assignment, the variable x refers to the integer object containing 7. As shown in snippet [6], snippet [5] does not change x’s value. You can change x as follows:

In [7]: x = x + 10

In [8]: x
Out[8]: 17

Python uses dynamic typing—it determines the type of the object a variable refers to while executing your code. We can show this by rebinding the variable x to different objects and checking their types:

In [9]: type(x)
Out[9]: int

In [10]: x = 4.1

In [11]: type(x)
Out[11]: float

In [12]: x = 'dog'

In [13]: type(x)
Out[13]: str

Python creates objects in memory and removes them from memory as necessary. After snippet [10], the variable x now refers to a float object. The integer object from snippet [7] is no longer bound to a variable. As we’ll discuss in a later chapter, Python automatically removes such objects from memory. This process—called garbage collection—helps ensure that memory is available for new objects you create.