CODEWITHSUNDEEP
pythonlistsortingdictionary
asimes
asimes

Reputation: 5894

Sort List of string based on value in Dict

I have a List of strings named frequentItems and a Dict named mis (Multiple Item Support value) whose values are floats. The relationship between the two is that any element of frequentItems, i is a key to mis so that mis[frequentItems[i]] returns a float value.

I would like to sort frequentItems based on the float values returned from mis[frequentItems[i]] but am unsure how to specify this using .sort() or sorted(). I have basically no experience using lambda but think it is what I need to specify.

Upvotes: 1

Views: 766

Answers (2)

thefourtheye
thefourtheye

Reputation: 239463

You don't even need the lambda here, you can simply use dict.get to get the value corresponding to the elements of the list.

frequentItems.sort(key = mis.get)

Example:

mis, frequentItems = {1: 3.4, 5: 3.14, 3: 7.5}, [1, 3, 5]
frequentItems.sort(key = mis.get)
print(frequentItems)  # [5, 1, 3]

Upvotes: 4

Joran Beasley
Joran Beasley

Reputation: 113948

def getItem(itemName):
    return mis.get(itemName)

frequentItems.sort(key=getItem)

you could of coarse rewrite getItem as a lambda function

getItem = lambda itemName:mis.get(itemName,None)
frequentItems.sort(key=getItem)

you could include it as key directly as a lambda 

frequentItems.sort(key= lambda itemName:mis.get(itemName,None))

you could simplify your argument to a single letter

frequentItems.sort(key= lambda i:mis.get(i,None))

while the lambdas are shorter they can be slower

(or use thefourtheye's much better solution for this actual problem :P)

Upvotes: 1

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