declaring a python variable in a list [data] = self.read()?

Question

while studying the open source repo of Odoo I found a line of code that I don't understand like the following

[data] = self.read()

found there https://github.com/odoo/odoo/blob/8f297c9d5f6d31370797d64fee5ca9d779f14b81/addons/hr_holidays/wizard/hr_holidays_summary_department.py#L25

I really would like to know why would you put the variable in a list

Answer 1

It seems to ensure that [data] is an iterable of one item and therefore unpacks the first value from self.read()

It cannot be assigned to a non-iterable

>>> [data] = 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot unpack non-iterable int object

Works for iterable types, though must have a length equal to one

>>> [data] = {'some':2}
>>> data
'some'
>>> [data] = {'foo':2, 'bar':3}
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: too many values to unpack (expected 1)
>>> [data] = [1]
>>> data
1
>>> [data] = [[1]]
>>> data
[1]
>>> [data] = [1, 2]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: too many values to unpack (expected 1)
>>> [data] = []
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: not enough values to unpack (expected 1, got 0)