Objects and Naming

Understanding objects and naming in Python can be difficult. In this demo we'll follow a post Is Python call-by-value or call-by-reference? Neither..

First, let's make some objects. Everything in Python is an object.

#So when we make a string it's an object. When we call it a variable name, it binds that name to the string object. 
fruit = 'apple'

#When we make a list, it will point to the object bound by fruit
lunch = []
lunch.append(fruit)

dinner = lunch
dinner.append('fish')

fruit = 'pear'

meals = [fruit, lunch, dinner]
print(meals)

Let's check the object ids for both lists

print(id(lunch))
print(id(dinner))

Notice what happens when we append to list that is bound to both lunch and dinner:

dinner.append('pasta')
print(lunch, dinner)

lunch.append('carrots')
print(lunch,dinner)

Mutable and Immutable

We've looked at mutable and immutable. Tuples are an example of immutable objects.

fruits = ['apple', 'banana', 'orange']
veggies = ['carrot', 'broccoli']

food_tuple = (fruits, veggies)

print(food_tuple)

fruits.append('plum')

print(fruits)

print(food_tuple)

So we can't change a tuple, but we can change the (mutable) things that a tuple element points to.

Iclicker question

Anna = ['electrical']
Julie = Anna
Julie += ['physics']
print(Anna)