On the question of how variables can be passed to functions, C, of
course, has the & operator and Pascal has the "var" keyword.
An analogous thing can be achieved in Python 3 (but not in Python 2, I'm
afraid). The & operator corresponds to an ad hoc property class as in
the program below (not intended to be serious).
The program demonstrates how to write a universal "swap" function that
interchanges two references.
Marko
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#!/usr/bin/env python3
import sys
def main():
some_list = [ 'a', 'b', 'c' ]
some_dict = { 'few' : 'ding',
'good' : 'dang',
'men' : 'dong' }
some_value = 'certainly'
class SomeListElementProperty:
"""&some_list[1]"""
def get(self):
return some_list[1]
def set(self, value):
some_list[1] = value
class SomeDictEntryProperty:
"""&some_dict["men"]"""
def get(self):
return some_dict['men']
def set(self, value):
some_dict['men'] = value
class SomeValueProperty:
"""&some_value"""
def get(self):
return some_value
def set(self, value):
nonlocal some_value
some_value = value
swap(SomeListElementProperty(), SomeDictEntryProperty())
swap(SomeListElementProperty(), SomeValueProperty())
sys.stdout.write("{}\n".format(some_list))
sys.stdout.write("{}\n".format(some_dict))
sys.stdout.write("{}\n".format(some_value))
def swap(px, py):
x = px.get()
y = py.get()
px.set(y)
py.set(x)
if __name__ == '__main__':
main()
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