Python Avoid Nested For Loop

Question

I am new to python programming and I am getting my hands dirty by working on a pet project.

I have tried a lot to avoid these nested for loops, but no success.

Returns values from a for loop in python

import requests
import json

r = requests.get('https://api.coinmarketcap.com/v1/ticker/')
j = r.json()


for item in j:
    item['id']
    n = item['id']
    url = 'https://api.coinmarketcap.com/v1/ticker/%s' %n
    req = requests.get(url)
    js = req.json()
    for cool in js:
        print n
        print cool['rank']

Please let me know if more information is needed.

Sometimes you need nested for loops. This looks like one of those times. — mechanical_meat
– mechanical_meat, Commented Jun 9, 2017 at 16:13
I am getting a lot of data and having nested for loop is too time consuming :( I understand your point though. Thank you for the feedback. — Master
– Master, Commented Jun 9, 2017 at 16:20
To avoid writing a nested loop, you could create a function to parse js that contains the inner for loop. Note that this would still technically contain nested loops, but your code will at least appear flatter. — Jared Goguen
– Jared Goguen, Commented Jun 9, 2017 at 16:20
@Master The reason of getting rid of nested for-loop is usually to make it more readable or easier to maintain. It will seldom improve speed. — kennytm
– kennytm, Commented Jun 9, 2017 at 16:21
@Master Are you requesting the same url repeatedly? It looks like the only way to reduce complexity/time would be to reduce the number of requests. If each request is unique, I'm not sure how you could do that. — Jared Goguen
– Jared Goguen, Commented Jun 9, 2017 at 16:21

Anton Panchishin · Accepted Answer · 2017-06-09 16:39:44Z

1

Question

I have too many loops in loops and want a python way of cleaning it up

Answer

Yes, there is a python way of cleaning up loops-in-loops to make it look better but there will still be loops-in-loops under-the-covers.

import requests
import json

r = requests.get('https://api.coinmarketcap.com/v1/ticker/')
j = r.json()

id_list = [item['id'] for item in j]

for n in id_list:
    url = 'https://api.coinmarketcap.com/v1/ticker/%s' %n
    req = requests.get(url)
    js = req.json()
    print "\n".join([ n+"\n"+item['rank'] for item in js ])

Insight from running this

After running this specific code, I realize that your are actually first retrieving the list of tickers in order of rank using

r = requests.get('https://api.coinmarketcap.com/v1/ticker/')

and then using

url = 'https://api.coinmarketcap.com/v1/ticker/%s' %n

to get the rank.

So long as the https://api.coinmarketcap.com/v1/ticker/ continues to return the items in order of rank you could simplify your code like so

import requests
import json

r = requests.get('https://api.coinmarketcap.com/v1/ticker/')
j = r.json()

id_list = [item['id'] for item in j]

result = zip(id_list,range(1,len(id_list)+1) )

for item in result :
print item[0]
print item[1]

Answer to addition question

Addition question : What if I want one more parameter say price_usd? ..... for cool in js: print n print cool['rank'] print cool['price_usd']

Answer :

change the line

print "\n".join([ n+"\n"+item['rank'] for item in js ])

to

print "\n".join([ n+"\n"+item['rank']+"\n"+cool['price_usd'] for item in js ])

edited Jun 9, 2017 at 16:39

answered Jun 9, 2017 at 16:26

Anton Panchishin

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5 Comments

Master Over a year ago

What if I want one more parameter say price_usd? ..... for cool in js: print cool['price_usd']

Anton Panchishin Over a year ago

I updated the response to have the additional answer.

Master Over a year ago

thank you for the input and explaining a pythonic way to write a code :)

Anton Panchishin Over a year ago

don't say thanks, just upvote and/or accept the answer. cheers

Master Over a year ago

Well I can't upvote because my reputation is too low. Also, Jared Goguen's response saves me a lot of execution time :) But, I appreciate your efforts to help me out.

Jared Goguen · Accepted Answer · 2017-06-09 16:38:58Z

0

Your first request already gets you everything you need.

import requests
import json

response = requests.get('https://api.coinmarketcap.com/v1/ticker/')
coin_data = response.json()

for coin in coin_data:
    print coin['id'] # "bitcoin", "ethereum", ...
    print coin['rank'] # "1", "2", ...
    print coin['price_usd'] # "2834.75", "276.495", ...

answered Jun 9, 2017 at 16:38

Jared Goguen

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1 Comment

Master Over a year ago

Respect. Appreciate the response.

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