Foreach in python

If you are coming from php, you used to use "foreach" to iterate arrays or objects. This is used and some other languages too, such as JavavaScript for example. Foreach in python is a bit different.

How to iterate a list in python?

list_with_fruits = ["grapes", "lime", "lemon", "cherry", "blueberry", "banana"]

Print the list before iterating(this is not mandatory)

print(list_with_fruits)

Now let's iterate through the list

print("iterating a basic list")

for fruit in list_with_fruits:
    print(fruit)

If you want to gain access to the fruit index as well you can use the enumerate function to do it

print("iterating a list with index")

for index, fruit in enumerate(list_with_fruits):
    print("index", index, "fruit", fruit)

multidimensional_list = [
    ["grapes", "lime", "lemon", "cherry", "blueberry", "banana"],
[   "Mercedes-Benz", "Toyota", "Volkswagen", "BMW", ],
    ["tiger", "lion", "elephant ", ]
    ]
for i, item in enumerate(multidimensional_list):
    # separate each list with 50 *
    print("*" * 50) # display 50 *
    for j, name in enumerate(item):
        print("Location: ", i,j, "Item Name: ",  name)

So if you want to access fruits list you will have to do something like

print(multidimensional_list[0])

Then for the other one

print(multidimensional_list[1])
print(multidimensional_list[2])

This is what the first for is doing basically item is replacing multidimensional_list[0] with the item at first iteration then item = multidimensional_list[1] and so on

So now we know that item is a list, and you already know how to iterate a list

If you don't need an index on each fruit, cars, or animals, you could use the simple version without enumerate

 for name in item:
     print("Item Name: ", name)

In the same way you can iterate through a tuplet

list_with_fruits = ("grapes", "lime", "lemon", "cherry", "blueberry", "banana")

for fruit in list_with_fruits:
    print(fruit)

same thing applies for index

for index, fruit in enumerate(list_with_fruits):
    print("index", index, "fruit", fruit)

list_with_fruits = {"grapes": 30, "lime": 50, "lemon":60, "cherry":70, "blueberry":100, "banana":5}

If you use the same approach with dictionaries then only the key will be displayed

for fruit in list_with_fruits:
    print(fruit)

Again if you use the same approach you used on the list, the index will be displayed instead of the value

for index, fruit in enumerate(list_with_fruits):
    print(fruit, index)

So if you wanna display the key and the value use the items() method

for  fruit, nr in list_with_fruits.items():
    print( fruit, nr)

if the list is changing while you iterate you can create a copy of the list and delete from original list

list_with_fruits = ["grapes", "lime", "lemon", "cherry", "blueberry", "banana"]

for i, fruit in enumerate(list_with_fruits.copy()):

    if fruit == 'lime':
        del list_with_fruits[i]

print(list_with_fruits)

or you can create a new object while you iterate

list_with_fruits = ["grapes", "lime", "lemon", "cherry", "blueberry", "banana"]

new_fruit_list = []
for i, fruit in enumerate(list_with_fruits):

    if fruit != 'lime':
        new_fruit_list.append(list_with_fruits[i])

print(new_fruit_list)

How to iterate dicts in python?

Now let's convert our multidimensional list into a mix of tuplets, list and dicts

multidimensional_obj = {
    "fruits": ["grapes", "lime", "lemon", "cherry", "blueberry", "banana"],
    "cars": [   "Mercedes-Benz", "Toyota", "Volkswagen", "BMW" ],
    "animals": ("tiger", "lion", "elephant " )
    }

First let's iterate the dict

for key, items in multidimensional_obj.items():
    print("*" * 50)
    print("*", key)
    for label in items:
        print(f"*** {label}")

You can nest it on several levels but keep in mind that this nr is not limited

 

F.A.Q.

Why do I get the error "SyntaxError: too many statically nested blocks"

This limit applies to all other control flow blocks as well.

The limit for the number of nested control flow blocks is defined inside of code.h with a constant named CO_MAXBLOCKS.

If you have any questions feel free to contact me, I will update this tutorial if is the case