• You can use itertools.groupby to group the items by order number.

• Don't use is to compare numbers. is checks object identity and the same can be represented by different objects:

   >>> a=1234
   >>> b=1234
   >>> a is b
   False
   >>> a=12
   >>> b=12
   >>> a is b
   True                
  

• Checking if len(orders) > 0 before the for loop is redundant. If the list is empty the loop won't run even once.

Revised code:

from itertools import groupby
from operator import itemgetter
        
# Fetch my orders
orders = repo.get_orders_for(self._customer[0])

for order_number, items in groupby(orders, key=itemgetter(0)):
    print("Order #{}".format(order_number))
    for _, quantity, pid in items:
        print("    Product #{}, ordered x{}".format(pid, quantity))     

• You can use itertools.groupby to group the items by order number.

• Don't use is to compare numbers. is checks object identity and the same number can be represented by different objects:

   >>> a=1234
   >>> b=1234
   >>> a is b
   False
   >>> a=12
   >>> b=12
   >>> a is b
   True                
  

• Checking if len(orders) > 0 before the for loop is redundant. If the list is empty the loop won't run even once.

Revised code:

from itertools import groupby
from operator import itemgetter
        
# Fetch my orders
orders = repo.get_orders_for(self._customer[0])

for order_number, items in groupby(orders, key=itemgetter(0)):
    print("Order #{}".format(order_number))
    for _, quantity, pid in items:
        print("    Product #{}, ordered x{}".format(pid, quantity))