On 14/11/2019 17:11, R.Wieser wrote:
Rhodri,
MyVar is a global here, so nonlocal explicitly doesn't pick it up.
I do not agree with you there (the variable being global). If it where than
I would have been able to alter the variable inside the procedure without
having to resort to a "global" override (an override which is only valid for
the context its used in by the way, not anywhere else)
Than again, that is how it works in a few other languages, so I might have
been poisonned by them.:-)
You have been.
# This is at the top level of a module
# I.e. it's a global variable
my_global_variable = 5
# You can read globals from within a function without declaring them
def show_my_global():
print(my_global_variable)
# If you try setting it, you get a local instead
def fudge_my_global(n):
my_global_variable = n
show_my_global() # prints '5'
fudge_my_global(2)
show_my_global() # prints '5'
# If you read the variable before setting it, you get an exception
def mess_up_my_global(n):
print(my_global_variable)
my_global_variable = n
mess_up_my_global(2) # UnboundLocalError!
# ...because it must be a local because of the assignment, but it
# doesn't have a value at the time print() is called.
# To do it right, declare you want the global from the get go
def love_my_global(n):
global my_global_variable
print("It was ", my_global_variable)
my_global_variable = n
love_my_global(3) # prints 'It was 5'
show_my_global() # prints '3'
--
Rhodri James *-* Kynesim Ltd
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