For example:
names = ['Rodrigo', 'Matthew', 'Adam', 'Will']
def get_len(name):
return len(name)
print(max(names, key=get_len))
print(min(names, key=get_len))
# or
print(max(names, key=lambda name : len(name)))
print(min(names, key=lambda name : len(name)))
How do I know whether it is possible or not possible to use a function as a ‘key=func’ argument?
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Answer
As indicated in the documentation, min() (and max()) expect a one-argument ordering function like that used for list.sort(). https://docs.python.org/3/library/functions.html#min
So, what’s expected is a function that takes a single argument from the collection that min() or max() is applied to and that returns a single value that can be ordered with < and >.
So, for names, which is a list of strings, that would be a function that takes a single str as an argument and returns something that is comparable using < or > to order the strings, for example its length.
So, even this would work:
names = ['Rodrigo', 'Matthew', 'Adam', 'Will'] print(max(names, key=len))
To answer your general question “How do I know whether it is possible or not possible to use a function as a key argument to min()?”
You check if the function:
- accepts a single argument
- the type of the argument matches the type of the elements of the collection
min()will be applied to - returns a value that can be ordered using
<and>