defaultdict clear solution for Call to Home by ciel - python coding challenges

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defaultdict solution in Clear category for Call to Home by ciel

from collections import defaultdict
from operator import methodcaller
def total_cost(calls):
    d=defaultdict(int)
    for e in map(methodcaller('split'),calls): d[e[0]]+=(int(e[2])+59)//60
    return sum(e if e<100 else 100+2*(e-100) for e in d.values())

May 21, 2014

Comments:

artemrudenko on Aug. 19, 2014, 10:39 a.m.
Never read about methodcaler - thank you for an idea.

suic on Feb. 6, 2015, 6:47 p.m.
Hi, I didn't know about method caller. Thanks.

veky on Feb. 14, 2015, 8:52 a.m.
As you see from the comments, methodcaller is good from educational point of view. :-) But there is a much easier way: just use unbound method. <pre class='brush: python'>map(str.split, calls) </pre>

ciel on Feb. 14, 2015, 4:39 p.m.
Cool... Actually I didn't know 'abc'.split('b') === 'abc'.__class__.split('abc','b') until recently. Python's object handling is quite much different from Ruby's :p

veky on Feb. 14, 2015, 5:14 p.m.
Yes, here Ruby is correct, and Python is practical. :-] BTW you don't write `x.len()`, you write `len(x)`, right? So write `type(x)` instead of `x.class`. ;-)

ciel on Feb. 14, 2015, 5:54 p.m.
Looks like I have learned a new function... ^_^

veky on Feb. 14, 2015, 7:53 p.m.
While we're at it, you could learn another one... You used to write `x.dict`? Probably you didn't know it's nicer written as `vars(x)`. ;-)

texom512 on Aug. 1, 2015, 9:44 p.m.
You're right, it's much easier!

texom512 on Aug. 1, 2015, 9:48 p.m.
It's not a good idea to import methodcaller for one use... That's better: [call.split() for call in calls] or the veky's solution: map(str.split, calls) And seriously you don't have to remove all spaces! A clear code is not a short code ;-).

veky on Aug. 1, 2015, 11:42 p.m.
[call.split() for call in calls] is not the same as map... (call.split() for call in calls) is much more like it - since it's not a list, but a generator.

texom512 on Aug. 2, 2015, 1:55 p.m.
Thanks, but why a generator rather a list? For the memory?

veky on Aug. 2, 2015, 4:58 p.m.
What do you mean by "why a"? Why map gives a generator instead of a list in Py3? Yes, "for the memory" mostly, but also a philosophical point. Not every sequence is a list, and sometimes things like tuple are more appropriate. Just say what you want explicitly: `list(map(...))`. In Py3.5, you can also write it as a "star comprehension": `[*map(...)]`. More importantly, not everytime you need to freeze the values all together (at the same time at different places), you want to iterate through them (at same place at different times). This time/space duality is completely supported in modern Python.

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