Group array by the first element value Python

Question

i have an Array arr = [title, fileurl] so when i do print arr it goes like this:

['name1', 'url1']
['name1', 'url2']
['name1', 'url3']
['name2', 'url1']
['name2', 'url2']
['name3', 'url1']

I would like to group these array by the first element, it means I would like to have:

['name1', 'url1', 'url2', 'url3']
['name2', 'url1', 'url2']
['name3', 'url1']

My code:

for final in posterlink:
    pagesourcec = requests.get(final)
    soupc = BeautifulSoup(pagesourcec.text, "html.parser")
    strc = soupc.findAll("iframe", attrs={"id": "myframe"})
    title = soupb.find("li",{"class": "breadcrumb-item active"}).get_text()
    for embedlink in strc:
        fff = embedlink.get('data-src')
        arr = [title, fff]
        print arr

Do you really need an array? Would not it be better with a dictionary instead? so you could have at the end `{"name1": ["url1", "url2", "url3"], "name2": ["url1", "url2"]}` — Manuel Sánchez, Nov 21 '18 at 11:22
sorry it's variable title = soupb.find("li",{"class": "breadcrumb-item active"}).get_text() — Lalmi Mohammed Issam, Nov 21 '18 at 11:24

Silver · Answer 1 · 2018-11-22T07:47:59.023

You can do this:

from collections import defaultdict as ddict

group = ddict(list)

for name, url in arr:
  group[name].append(url)

And if you absolutely want it as a list of lists, you can then follow up with this:

group = [[name, *urls] for name, urls in group.items()]

Edit: It's important to note that the above line works with python 3, which is what you should be using anyways. However, for the sake of completeness if you're using python 2.7, then use this:

group = [[name] + urls for name, urls in group.items()]

Rohit-Pandey · Answer 2 · 2018-11-21T11:43:03.557

-2

Try This:

a = [['name1', 'url1'],
 ['name1', 'url2'],
 ['name1', 'url3'],
 ['name2', 'url1'],
 ['name2', 'url2'],
 ['name3', 'url1']]
d = {}
for elem in a:
    if elem[0] not in d:
        d[elem[0]] = []
    d[elem[0]].append(elem[1:])

Output:

{'name1': [['url1'], ['url2'], ['url3']], 'name2': [['url1'], ['url2']], 'name3': [['url1']]}

edited Nov 21 '18 at 11:43

answered Nov 21 '18 at 11:28

Rohit-Pandey

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You should not use `dict` as variable name – Andersson Nov 21 '18 at 11:29
Now @Andersson. – Rohit-Pandey Nov 21 '18 at 11:35
Now the dict name is OK, but it still not clear what your code should do... What is `a`? Is it list of lists? Also the output not really looks like the one that OP is looking for – Andersson Nov 21 '18 at 11:38
Now Fully Updated with `a`. btw `a ` is lists of list. – Rohit-Pandey Nov 21 '18 at 11:43
IMO instead of re-formatting data it's better to get data in correct format initially... Also your key values are not lists of elements, but lists of lists with single element - still doesn't look like OP requirements met... – Andersson Nov 21 '18 at 11:46
@Andersson for getting desired output user can play with list. – Rohit-Pandey Nov 21 '18 at 12:13

Group array by the first element value Python

2 Answers2