Get max key value pair from dictionary, but with key restrictions-CodePudding

Imagine I have a dictionary like this:

{(0,0) : 5 , (0,1) : 7 , (0,2) : 9 , (1,0) : 1 , (1,1) : 3 , (1,2) : 20 , (2,0) : 6 , (2,1) : 5 , (2,2) : 25 }

Is there a way to get the max key value pair, but with only taking into account keys with certain values?

For example, if I wanted the max pair from when the first index of the key is 0. So the max between:

 {(0,0) : 5 , (0,1) : 7 , (0,2) : 9}

Which would be (0,2) : 9

CodePudding user response：

You can use a comprehension with an if clause to get all the relevant elements, and then get the max value with max():

max(value for key, value in d.items() if key[0] == 0)

A more general case would be something like:

max(value for key, value in d.items() if predicate(key, value))

Where predicate is some function which returns a boolean.

For getting both the key and value, you can use the following:

d = {(0,0) : 5 , (0,1) : 7 , (0,2) : 9 , (1,0) : 1 , (1,1) : 3 , (1,2) : 20 , (2,0) : 6 , (2,1) : 5 , (2,2) : 25 }
max_key = max({k: v for k, v in d.items() if k[0] == 0}, key=d.get)
max_value = d[max_key]

Note that there may be several keys with the max value.

CodePudding user response：

We could use filter to filter out the required keys from the original dictionary. In this case, keys which have 0 at the 0th index.

def filter_function(item):
    key, value = item
    return key[0] == 0

def max_key(item):
    key, value = item
    return value

print(max(filter(filter_function, dictionary.items()), key=max_key))

The filter_function could be replaced with whatever condition you'd like to have.