Map an array to each item in another array? (Python)

Question

I'm trying to generate some predictable URL's for a crawler.

I have a set of base urls:

base_urls = ['http://something.com/john', 
             'http://something.com/sally']

and each one has a unique url for their daily calendar:

to_append = ['-mon-calendar', 
             '-tues-calendar', 
             '-wed-calendar', 
             '-thurs-calendar', 
             '-fri-calendar']

I need to generate a new array containing a complete list of the all people's weekly calendars (e.g. 'http://something.com/john-mon-calendar',...

I could iterate through this the long way but assume it's possible to do it more efficiently with map(). I haven't used map much and doing it with two iterables is throwing me off. Could anyone point me in the right direction?

Cory Kramer · Accepted Answer · 2015-11-14 20:53:17Z

8

You can use itertools.product to create the Cartesian product between your lists, then join each item within a list comprehension.

>>> from itertools import product
>>> [''.join(i) for i in product(base_urls, to_append)]
['http://something.com/john-mon-calendar',
 'http://something.com/john-tues-calendar',
 'http://something.com/john-wed-calendar',
 'http://something.com/john-thurs-calendar',
 'http://something.com/john-fri-calendar',
 'http://something.com/sally-mon-calendar',
 'http://something.com/sally-tues-calendar',
 'http://something.com/sally-wed-calendar',
 'http://something.com/sally-thurs-calendar',
 'http://something.com/sally-fri-calendar']

answered Nov 14, 2015 at 20:53

Cory Kramer

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Jason · Accepted Answer · 2015-11-14 20:57:34Z

1

No libraries:

links = [[url + day for day in to_append] for url in base_urls]
links_flattened = sum(links, [])

answered Nov 14, 2015 at 20:57

Jason

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