Python loop through array and add to initial array

Language Help Python
,
1

Hello!
I was working on this exercise: https://www.codecademy.com/courses/learn-python-3/lessons/create-python-list/exercises/append-list
And I have a question. It may be dumb :slight_smile:
Why does

def add_order(new_orders):
  orders = ["daisies", "periwinkle"]
  for x in new_orders:
     orders.append(x) 
  return orders

print(add_order(['tulips']))
print(add_order(['roses']))

return

['daisies', 'periwinkle', 'tulips']
['daisies', 'periwinkle', 'roses']

I heard that .append generally modifies the original array, so when calling add_order(['roses']), why it is not [‘daisies’, ‘periwinkle’, ‘tulips’, ‘roses’]?

2

It’s not a dumb question.

Roses is not part of the original list (orders).
You’re adding one item to the end of the original list. .append() only adds a single item or object at a time.

3

Ok. Thank you. Can you recommend what I should use to achieve my goal?

4

You could use the “+” sign to add new items.

Summary 
def add_order(new_orders):

  orders = ["daisies", "periwinkle"] + new_orders
  
  return orders

print(add_order(['tulips', 'roses', 'daffodils']))
>>>['daisies', 'periwinkle', 'tulips', 'roses', 'daffodils']

If you didn’t want to write a function you could use .extend() which adds all items from the iterable.

Summary 
orders = ["daisies", "periwinkle"] 
orders.extend(['tulips'])
orders.extend(['roses'])
print(orders)
>>['daisies', 'periwinkle', 'tulips', 'roses']

See:
https://docs.python.org/3/tutorial/datastructures.html#more-on-lists

1 Like
5

thank you!!!

1 Like