CODEWITHSUNDEEP
python
jonas
jonas

Reputation: 27

How to get the smallest item from the second items of a tuple list?

First of all sorry for the confusing title, I had no idead how to explain my problem without an example.

I have the following graph

graph = {
    1: [(3, 5), (4, 1),  (5, 4)],
    2: [(5, 9)],
    3: [(5, 1), (6, 1)],
    4: [(2, 11), (8, 2)],
    5: [(4, 6), (2, 6)],
    6: [(7, 1)],
    7: [(5, 7), (2, 1)],
    8: [(2, 6)],
}

I want to be able to get the smallest number from the second item of the tupels for a given number. For example, if I gave the function the number 1 I would want it to return the 1 from the second tupel. If the input was 4 instead I would expect it to return a 2 form the second tupel.

My current approach is min((graph[s])[1]), but this doesn't really work and mostly returns Index Errors.

Edit: I solved the problem with (min(graph[s])[0], min(graph[s])[1])[1] now (for some reason) it works in all cases (the problems were with lists that only contained one tupel).

Upvotes: 0

Views: 148

Answers (4)

TaQuangTu
TaQuangTu

Reputation: 2343

Just use:

s = 7
print(min(min(graph[s], key= lambda t:min(t))))

Upvotes: 1

Startiflette
Startiflette

Reputation: 111

min((graph[key])[1]) works for me.

You can try : min([x[1] for x in graph[key]])

Upvotes: 0

Gabio
Gabio

Reputation: 9504

Try this:

def get_smallest_num(key):
    return min(map(lambda x: x[1], graph[key]))

print(get_smallest_num(1)) # 1
print(get_smallest_num(5)) # 6

Upvotes: 0

azro
azro

Reputation: 54168

Your problem comes when dealing when pair like 2: [(5, 9)] where there is juse 1 item, when accessing [1] this will fail, you gotta check the length before

def get_min(graph, key, position=1):
    values = graph[key]
    if len(values) > position:
      return min(values[position])
    return -1


graph = {1: [(3, 5), (4, 1), (5, 4)],2:[(5, 9)],3: [(5, 1), (6, 1)],4: [(2, 11), (8, 2)],
         5: [(4, 6), (2, 6)],6: [(7, 1)],7: [(5, 7), (2, 1)],8: [(2, 6)],}

for k,v in graph.items():
  print(k, get_min(graph, k))

1 => 1
2 => -1
3 => 1
4 => 2
5 => 2
6 => -1
7 => 1
8 => -1

Upvotes: 0

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