Forward References
Like some other high-level languages, Python does not permit you to reference or call a function before it has been declared. We can try a few examples to illustrate this:
def foo():
print 'in foo()'
bar()
If we were to call foo() here, it will fail because bar() has not been declared yet:
>>> foo() in foo() Traceback (innermost last): File "<stdin>", line 1, in ? File "<stdin>", line 3, in foo NameError: bar
We will now define bar(), placing its declaration before foo()’s declaration:
def bar():
print 'in bar()'
def foo():
print 'in foo()'
bar()
Now we can safely call foo() with no problems:
>>> foo() in foo() in bar()
