[MRG] Update pytest

[wdevazelhes]

This makes us update to the lastest pytest

[wdevazelhes]

Apparently I used fixtures in a bad way sometimes, which was still supported in old pytest versions but not anymore so I deleted fixtures and replaced them by regular functions when needed

[wdevazelhes]

If I let tuples_no_prep here, I have an error saying tuples_no_prep is referenced before assignment... I didn't understand why ? Since tuples_no_prep is a function defined above in the module ? But changing into tuples_no_prep_bis it works
(I tried with a simple example and I still don't understand: for instance this script returns UnboundLocalError: local variable 'a' referenced before assignment when executed:

def a():
    return 5

def test():
    c = a()
    a = 3

if __name__ == '__main__':
    test()

Does python automatically detects that the variable "a" is assigned in "test" and that it must be a variable local to "test" ?)

[perimosocordiae]

Yeah, Python treats local variables specially at the bytecode level. Here's the result of dis.dis(test) using your example code:

  5           0 LOAD_FAST                0 (a)
              3 CALL_FUNCTION            0
              6 STORE_FAST               1 (c)

  6           9 LOAD_CONST               1 (3)
             12 STORE_FAST               0 (a)
             15 LOAD_CONST               0 (None)
             18 RETURN_VALUE

The LOAD_FAST opcode is specifically looking for a local variable named a, which is why you get the UnboundLocalError.

Changing the assignment of a to a different name results in a LOAD_GLOBAL opcode, which works as expected:

In [5]: def test2():
   ...:     c = a()
   ...:     b = 3
   ...:

In [6]: test2()

In [7]: dis.dis(test2)
  2           0 LOAD_GLOBAL              0 (a)
              3 CALL_FUNCTION            0
              6 STORE_FAST               0 (c)

  3           9 LOAD_CONST               1 (3)
             12 STORE_FAST               1 (b)
             15 LOAD_CONST               0 (None)
             18 RETURN_VALUE

You could also mark a global in the function, but this will result in overwriting the module-level function:

In [8]: def test3():
   ...:     global a
   ...:     c = a()
   ...:     a = 3
   ...:

In [9]: test3()

In [10]: test3()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-10-5dea5f7ba8cb> in <module>()
----> 1 test3()

<ipython-input-8-32a55428a886> in test3()
      1 def test3():
      2     global a
----> 3     c = a()
      4     a = 3
      5

TypeError: 'int' object is not callable

In [11]: dis.dis(test3)
  3           0 LOAD_GLOBAL              0 (a)
              3 CALL_FUNCTION            0
              6 STORE_FAST               0 (c)

  4           9 LOAD_CONST               1 (3)
             12 STORE_GLOBAL             0 (a)
             15 LOAD_CONST               0 (None)
             18 RETURN_VALUE

[wdevazelhes]

Very interesting, thanks ! :)

[perimosocordiae]

Merged, thanks!