Implementing forward declarations for functions in Python [duplicate]

Question

Is it possible to declare functions and implement them separately in python ? I mean something like in C :

void foo();



void foo() 
{

}

Answer 1

C forward declarations are used to work around dependency problems. Function foo is used by function bar, and foo needs bar to exist before you can declare it:

void bar()
{
    if (condition) { foo(); }
}

void foo() 
{
    if (condition) { bar(); }
}

won't compile because foo hasn't been declared yet; void foo(); is the C spelling for I know what I am doing, compiler, accept that foo will exist later.

There are no such dependency problems in Python, as global names are looked up at runtime; they don't have to yet exist at compile time.

In other words, this just works:

def bar():
    if condition: foo()

def foo():
    if condition: bar()

because bar and foo are resolved at runtime.

Answer 2

If your script is standalone you can use __name__=='__main__' to circumvent your problem with forward declaration read more.

Note that this is not really an answer to your question but a work around. Consider the following script as an example.

def main():
    bar()

def bar(): 
    print "Hello World"

if __name__=="__main__":
   main() # can be any function not necessarily "main"