Is there a way to use values in a list to search a dictionary?-CodePudding

I have a list of list that has values which are the same as some keys in a dictionary, like so:

list_a = [["a", "c", "e"], ["b", "f", "g"], ["b", "d", "i"]]
dict_a = {"a": "3", "b": "3", "c": "2", "d": "5", "e": "4", "f": "3", "g": "3", "h": "1", "i": "1"}

I want to use the values in list_a to access dict_a and check if the values by those keys are the same. To make myself clear: I take the first list in list_a and use those values to check if values in dict_a by keys "a", "c" and "e" share the same value. If yes (so if those three keys share the same values) do something, if not keep looking. So far I have tried different variations of this:

for i in range(len(list_a)):
check = list_a[i]
  for j in range(len(check)):
      if dict_a[check[j]] == "3":
        #do stuff

With no result other than doing the thing every time it find a correspondence. What am I missing?

CodePudding user response：

Use the all() function to check if all the values are the same.

And use any() to test if this is true for any of the sublists in list_a.

if any((all(dict_a.get(v) == dict_a.get(check[0]) for v in check) for check in list_a):
    # do stuff

CodePudding user response：

If you only need the first matching result you can get it in one line of code:

list_a = [['a', 'c', 'e'], ['b', 'f', 'g'], ['b', 'd', 'i']]
dict_a = {'a': '3', 'b': '3', 'c': '2', 'd': '5', 'e': '4', 'f': '3', 'g': '3', 'h': '1',
          '1': '1'}
if (result := next((sublist for sublist in list_a if len(set(dict_a.get(v, v) for v in sublist)) == 1), None)):
    # do stuff
    print(result)

The basic idea is to loop over all inner lists. Then we take each element of the inner list, get the corresponding value from the dictionary and build a set with all those values. If this set has only one element then all the values are the same. We return the element with next and provide a default value of None if no matching inner list could be found.

After your clarification that all those values must match a given value there is a different solution:

value_to_find = '3'
for sublist in list_a:
    if all(dict_a.get(value, value) == value_to_find for value in sublist):
        print(sublist)
        # your code here
        break

Remove the break if you want to perform the action on multiple inner lists if multiple inner lists match.

CodePudding user response：

list_a = [["a", "c", "e"], ["b", "f", "g"], ["b", "d", "i"]]
dict_a = {"a": "3", "b": "3", "c": "2", "d": "5", "e": "4", "f": "3", "g": "3", "h": "1", "i": "1"}
for i in range(len(list_a)):
    check = list_a[i]
    lst = [dict_a[check[j]] for j in range(len(check))]
    if lst[:-1] == lst[1:]:
        print("All same")
    else:
        print("Not All same")