Continuing my exploration of the itertools module in Python I wanted to look at the ifilter() method. ifilter() is a method that returns an iterator of items that return true from a test function (or lambda expression). In this sample I have an array of products. I want to get a list of products that have inventory in stock and are allowed to be drop-shipped.
import json
from itertools import ifilter
products = [
{"id": "SHIRT-BLU15", "category": "T-Shirt", "color": "Blue", "size": "large", "instock": 125, "backorder": 50, "shipTypes": ["tostore", "dropship"], "price": 25.99},
{"id": "SHIRT-BLU13", "category": "T-Shirt", "color": "Blue", "size": "small", "instock": 105, "backorder": 20, "shipTypes": ["tostore", "dropship"], "price": 23.99},
{"id": "SHIRT-RED15", "category": "T-Shirt", "color": "Red", "size": "large", "instock": 145, "backorder": 20, "shipTypes": ["tostore"], "price": 26.99},
{"id": "SHIRT-RED13", "category": "T-Shirt", "color": "Red", "size": "small", "instock": 25, "backorder": 75, "shipTypes": ["tostore"], "price": 20.99},
{"id": "SHIRT-GRN15", "category": "T-Shirt", "color": "Green", "size": "large", "instock": 102, "backorder": 0, "shipTypes": ["tostore", "dropship"], "price": 21.99},
{"id": "SHIRT-GRN13", "category": "T-Shirt", "color": "Green", "size": "small", "instock": 0, "backorder": 100, "shipTypes": ["tostore", "dropship"], "price": 21.99},
{"id": "SHIRT-PUR15", "category": "T-Shirt", "color": "Purple", "size": "large", "instock": 25, "backorder": 60, "shipTypes": ["tostore"], "price": 27.99},
{"id": "SHIRT-PUR13", "category": "T-Shirt", "color": "Purple", "size": "small", "instock": 0, "backorder": 100, "shipTypes": ["tostore"], "price": 26.99}
]
#
# Give me all shirts that are in stock and allow drop-ship
#
matches = [item for item in ifilter(lambda k: k["instock"] > 0 and "dropship" in k["shipTypes"], products)]
for i in matches:
print "Item ID %s is in stock and available for drop-ship" % i["id"]Much like most Python list and array manipulation methods I’m using a list comprehension here. The cool part is the call to ifilter(). The first argument is a lambda expression that checks the current item to see if we have a value greater than zero for instock, and if dropship is an item in the shipTypes array. The end result is an array of items that match, and I loop over that to show what’s available.
The more I use Python’s list comprehensions and the itertools module the more I find I like it! Cheers, and happy coding!