Loops in Python

Let's say you have a books array:

# data['books']:
[
	{ "name": 'Book 1', "price": 44.99, "qty": 1 },
	{ "name": 'Book 2', "price": 9.99, "qty": 3 },
	{ "name": 'Book 3', "price": 24.99, "qty": 2 }
]

"For" loops

At the post-processing step you may want to add 3 fields: In each book item add a total and formatted_total fields and calculate the order_total amount.

# Option 1. "For" loop
total = 0
for book in data['books']:
	book['total'] = book['price'] * book['qty']
	book['formatted_total'] = '$' + str(book['total'])
	total += book['total'] # accumulate order total
data['order_total'] = total

"For" loops with indexes

Alternatively, you can use a "for" loop with indexes:

# Option 2. "For" loop with indexes
total = 0
for index, book in enumerate(data['books']):
	book_total = book['price'] * book['qty']
	data['books'][index]['total'] = book_total
	data['books'][index]['formatted_total'] = '$' + str(book_total)
	total += book_total
data['order_total'] = total

"For" loops with range

... or using the range function:

# Option 3. "For" loop with range
total = 0
books_cnt = len(data['books']) # books_cnt = 3
for ind in range(0, books_cnt):
	book = data['books'][ind]
	book['total'] = book['price'] * book['qty']
	book['formatted_total'] = '$' + str(book['total'])
	total += book['total']
data['order_total'] = total

Now the data dictionary should look like this:

{
  "books": [
    {
      "name": "Book 1",
      "price": 44.99,
      "qty": 1,
      "total": 44.99,
      "formatted_total": "$44.99"
    },
    {
      "name": "Book 2",
      "price": 9.99,
      "qty": 3,
      "total": 29.97,
      "formatted_total": "$29.97"
    },
    {
      "name": "Book 3",
      "price": 24.99,
      "qty": 2,
      "total": 49.98,
      "formatted_total": "$49.98"
    }
  ],
  "order_total": 124.94
}

Iterate over fields

Finally, in some complex cases you may want to iterate over each parsed field:

for field_name, field_value in data.items():
	# your code goes here