get tuple list element by string name in python

Question

I have the following tuple list: It is for choice fields in a django model.

ENTITY_TYPE_CHOICES = (
    (0,'choice1'),
    (1,'choice2'),
)

I want to get the choices by their string name like:

entity_type_index = ENTITY_TYPE_CHOICES['choice1']

I get the error:

tuple indices must be integers, not str

Possible duplicate of [Tuple value by key](https://stackoverflow.com/questions/8731231/tuple-value-by-key) — Mike Scotty, Jun 17 '17 at 19:56
As said, tuples elements must be accessed by their position, so a number. You may want to try a dictionary instead? — swiss_knight, Jun 17 '17 at 19:56

Ajax1234 · Accepted Answer · 2017-06-17T20:08:20.810

2

You can build a dictionary:

ENTITY_TYPE_CHOICES = (
(0,'choice1'),
(1,'choice2'),
)

ENTITY_TYPE_CHOICES = dict([i[::-1] for i in ENTITY_TYPE_CHOICES])

entity_type_index = ENTITY_TYPE_CHOICES['choice1']

Output:

If you cannot use a dictionary:

new_choice = [i[0] for i in ENTITY_TYPE_CHOICES if i[1] == 'choice1']

print new_choice[0]

edited Jun 17 '17 at 20:08

answered Jun 17 '17 at 19:57

Ajax1234

69,937
8
61
102

What is wrong with this answer? I see this completely fine. – Mr. Xcoder Jun 17 '17 at 20:02
@Mr.Xcoder: I'm just guessing: The choice field in a django model has to be a tuple, not a dict. – Matthias Jun 17 '17 at 20:06

score 2 · Answer 2 · answered Jun 17 '17 at 20:05

You can iterate through the tuple. Tuple objects can only be accessed by indexes, not elements (as dictionaries)

ENTITY_TYPE_CHOICES = (
    (0,'choice1'),
    (1,'choice2'),
)

choice = 0

for i in ENTITY_TYPE_CHOICES:
 if i[1] == "choice1":
  choice = i[0]

If you now print it:

print(choice)  # Output: 0

And you can now use it with choice.

score 0 · Answer 3 · edited Jun 17 '17 at 20:07

0

You can find the index of the choice using ENTITY_TYPE_CHOICES.index('choice1')

Then you can use the number it gives to access it, by using:

 ENTITY_TYPE_CHOICES[ENTITY_TYPE_CHOICES.index('choice1')]

edited Jun 17 '17 at 20:07

Mr. Xcoder

4,719
5
26
44

answered Jun 17 '17 at 20:00

James

91
8

Linch · Answer 4 · 2017-06-17T20:07:53.693

Type of ENTITY_TYPE_CHOICES is tuple, but you use it as dict.

you can write method for iterate over tuple and find key:

get_entity_type_index(k):
    for index, key in ENTITY_TYPE_CHOICES:
         if key == k: return index

But this way is not the best practice.

Base on @Ajax1234 answer:

ENTITY_TYPE_CHOICES = (
   (0,'choice1'),
   (1,'choice2'),
)

ENTITY_TYPE_CHOICES_INDEX = {value: key for key, value in ENTITY_TYPE_CHOICES} 

print(ENTITY_TYPE_CHOICES_INDEX['choice2']) # output: 1

get tuple list element by string name in python

4 Answers4