CODEWITHSUNDEEP
pythonlistdictionary
Waqas_14
Waqas_14

Reputation: 31

Check if a List Element Exists in Dictionary Values

I have a list and a dictionary, and I need to check if elements of the list exist in the dictionary. If yes, I need to copy the key-value pair to a new dictionary, and discard the rest from the dictionary.

list0 = [
    -0.2385384148158066,
    -0.2307061452151448,
    -0.2150726345799602,
    -0.2138622652947372,
    -0.1098235264547504,
    -0.1072424768342444,
    -0.1037212327115436,
    -0.0966926943378552,
    -0.09614853460521154,
    9.353161396230564e-07
]
dict0 = {
    67: 1.440192237446893e-05,
    91: -0.1037212327115436,
    115: -0.2307061452151448,
    172: 0.0002879308975510175,
    242: 1.340170610273099e-05,
    266: -0.09614853460521154,
    290: -0.2138622652947372,
    347: 9.353161396230564e-07,
    417: 1.462739691486375e-05,
    441: -0.1072424768342444,
    465: -0.2385384148158066,
    513: 0.001208308075300354,
    606: -0.1098235264547504,
    630: -0.2442794187837403,
    677: 0.0007379497093922571,
    747: 1.336163063745514e-05,
    771: -0.0966926943378552,
    794: -0.2150726345799602
}

I tried iterating over the list and checking if the element is in dict0.values() and vice versa, but still couldn't figure out any way to access both key and value.

Upvotes: 0

Views: 414

Answers (3)

user17083192
user17083192

Reputation:

I'm not able to figure out why didn't you get the answer by iteration. You've not pasted your code, so I'm giving the answer in iteration method only so that you can compare it with your code. The code would be:

list0 = [
    -0.2385384148158066,
    -0.2307061452151448,
    -0.2150726345799602,
    -0.2138622652947372,
    -0.1098235264547504,
    -0.1072424768342444,
    -0.1037212327115436,
    -0.0966926943378552,
    -0.09614853460521154,
    9.353161396230564e-07
]
dict0 = {
    67: 1.440192237446893e-05,
    91: -0.1037212327115436,
    115: -0.2307061452151448,
    172: 0.0002879308975510175,
    242: 1.340170610273099e-05,
    266: -0.09614853460521154,
    290: -0.2138622652947372,
    347: 9.353161396230564e-07,
    417: 1.462739691486375e-05,
    441: -0.1072424768342444,
    465: -0.2385384148158066,
    513: 0.001208308075300354,
    606: -0.1098235264547504,
    630: -0.2442794187837403,
    677: 0.0007379497093922571,
    747: 1.336163063745514e-05,
    771: -0.0966926943378552,
    794: -0.2150726345799602
}
new_dict={}
for i in dict0:
    if dict0[i] in list0:
        new_dict[i]=dict0[i]
print(new_dict)

Upvotes: 0

Aatif Rashid
Aatif Rashid

Reputation: 15

Thats Pretty Simple to do:

This snippet may help:

new_dict={}
    for item in list0:
       for d in dict0:
          if(item==dict0[d]):
             new_dict[d]=item

Upvotes: 0

Selcuk
Selcuk

Reputation: 59184

You can use a dict comprehension:

>>> {k: v for k, v in dict0.items() if v in list0}
{91: -0.1037212327115436, 115: -0.2307061452151448, 266: -0.09614853460521154, 290: -0.2138622652947372, 347: 9.353161396230564e-07, 441: -0.1072424768342444, 465: -0.2385384148158066, 606: -0.1098235264547504, 771: -0.0966926943378552, 794: -0.2150726345799602}

If your list0 is very big, converting it to a set makes the above method faster:

>>> set0 = set(list0)
>>> {k: v for k, v in dict0.items() if v in set0}

Upvotes: 4

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