Why doesn't list have safe "get" method like dictionary?

Question

Why doesn't list have a safe "get" method like dictionary?

>>> d = {'a':'b'} >>> d['a'] 'b' >>> d['c'] KeyError: 'c' >>> d.get('c', 'fail') 'fail'  >>> l = [1] >>> l[10] IndexError: list index out of range 

Answer 1

Ultimately it probably doesn't have a safe .get method because a dict is an associative collection (values are associated with names) where it is inefficient to check if a key is present (and return its value) without throwing an exception, while it is super trivial to avoid exceptions accessing list elements (as the len method is very fast). The .get method allows you to query the value associated with a name, not directly access the 37th item in the dictionary (which would be more like what you're asking of your list).

Of course, you can easily implement this yourself:

def safe_list_get (l, idx, default):   try:     return l[idx]   except IndexError:     return default 

You could even monkeypatch it onto the __builtins__.list constructor in __main__, but that would be a less pervasive change since most code doesn't use it. If you just wanted to use this with lists created by your own code you could simply subclass list and add the get method.

Answer 2

This works if you want the first element, like my_list.get(0)

>>> my_list = [1,2,3] >>> next(iter(my_list), 'fail') 1 >>> my_list = [] >>> next(iter(my_list), 'fail') 'fail' 

I know it's not exactly what you asked for but it might help others.