Dynamic String formatting while looping - python

Question

I have been looking for a graceful way to dynamically format strings (URLs) in Python while looping... This is for when I want to request using different query parameters for each.

For example, this is what I've been resorting to at the moment (assuming I have 3 URLs):

for i in range(3):
    for num in range(0, 496, 5):
        if i == 1:
            requests.get('https://my-website.com?pricefrom={}&priceto={}'.format(num, num + 5))

        if i == 2:
            requests.get('https://my-website.com?qtyfrom={}&qtyto={}'.format(num, num + 5))

        # ......... :(

This is just ugly and I don't want to imagine what I'd do in the scenario where I have more links to request to.

Isn't there a solution simpler/more graceful like this for example:

urls = [<url1>, <url2>,....<url50>] # maybe each url has placeholders

for url in urls:
    # do some magic

Any help would be highly appreciated

you said different query params for each, can you post at least another variation of the url? thanks. — Lex Bryan
– Lex Bryan, Commented Jan 19, 2018 at 9:46
Why do you want to format strings when requests.get() let you pass the arguments as a dictionnary ? docs.python-requests.org/en/master/user/quickstart/… — bruno desthuilliers
– bruno desthuilliers, Commented Jan 19, 2018 at 9:57
Nice catch @brunodesthuilliers, but the thing is: a) I'm not always working with requests(I used it here for simplicity) b) Some of the urls have a lot more query params and I may need to change different parts of those which is why I prefer the string-formatting approach — Eb J
– Eb J, Commented Jan 19, 2018 at 13:11
@LexBryan Done .. Note: Slightly changed the first url as well — Eb J
– Eb J, Commented Jan 19, 2018 at 13:19

luminousmen · Accepted Answer · 2018-01-21 13:56:16Z

2

You can store strings with format in list as you said:

import requests

urls = ['https://example.com?from={fr}&to={to}',
        'https://example1.com?from={fr}&to={to}',
        'https://example2.com?from={fr}&to={to}'
]
for url in urls:
    for num in range(0, 496, 5):
        requests.get(url.format(fr=num, to=num + 5))

Also in python 3.6 you can use f-strings

edited Jan 21, 2018 at 13:56

answered Jan 19, 2018 at 9:38

luminousmen

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2 Comments

Eb J Over a year ago

Hey @luminousmen I tried this (even after adding the nested loop you forgot) but it wasn't working. Syntax error in the assignment of from and to in the format... Luckily, with a little tinkering, i found the solution... Thanks a million though..

luminousmen Over a year ago

Sorry @EbJ, wrote on a phone) Fix implementation

Eb J · Accepted Answer · 2018-01-20 08:08:13Z

0

Thanks to help from @luminousmen and the rest of you guys... I found a solution. Apparently you CAN just add placeholders and not do any operations on them :'D :

urls = ['https://example.com?from={}&to={}', 
        'https://example1.com?from={}&to={}',
        'https://example2.com?from={}&to={}']

for url in urls:
    for num in range(0, 496, 5):
        requests.get(url.format(num, num + 5))

edited Jan 20, 2018 at 8:08

answered Jan 20, 2018 at 8:03

Eb J

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