Why does a chained dictionary .get() in python return a tuple when the default provided is not a tuple?

Question

Python 2.6.6 when I call .get on the results of a .get the result is a tuple. This is making no sense to me. Example:

box = {}.get('test1',{}).get('test2','hrmm'),
print type(box)

prints out

<type 'tuple'>

this makes no sense to me. clearly the default in the second get is a simple string. so what gives? thanks for any insight.

score 38 · Accepted Answer · answered Nov 28 '12 at 23:48

38

You have a trailing comma at the end of the line, so you are getting the result of {}.get('test1',{}).get('test2','hrmm') in a one-element tuple.

Here is an example of how this works with a simple literal:

>>> box = 1,
>>> box
(1,)
>>> type(box)
<type 'tuple'>

answered Nov 28 '12 at 23:48

Andrew Clark

1

+1. Python doesn't have many traps for beginners, but the role of commas in the syntax for tuple literals is one of them. Usually it bites the other way around, though - people expecting `(foo)` to be a tuple containing `foo` when in fact it is just `foo`. This question demonstrates an amusing subversion of the typical mistake. – Mark Amery Nov 28 '12 at 23:59
Thank you kindly. I feel very silly right now. Ha Ha. Yes it makes sense of course now the comma would create a sequence type object of some kind. I completely was blind to see the trailing comma throughout many modifications and trials. – Blade McCool Nov 29 '12 at 01:05

score 6 · Answer 2 · answered Nov 28 '12 at 23:47

6

There is a trailing comma at your box assignment

answered Nov 28 '12 at 23:47

Jesse the Game

2 Answers2