In part 1, we looked at sending functions as arguments to other functions, at nesting functinons, and finally we wrapped a function in another function. We'll begin this part by giving an example implementation on the exercise I gave in part 1:
01.System Message: ERROR/3 (, line 11)
03.Unknown directive type "code".
05... code:: python
06.>>> def print_call(fn):
07.... def fn_wrap(*args, **kwargs):
08.... print("Calling %s with arguments: \n\targs: %s\n\tkwargs:%s" % (
09.... fn.__name__, args, kwargs))
10.... retval = fn(*args, **kwargs)
11.... print("%s returning '%s'" % (fn.func_name, retval))
12.... return retval
13.... fn_wrap.func_name = fn.func_name
14.... return fn_wrap
16.>>> def greeter(greeting, what='world'):
17.... return "%s %s!" % (greeting, what)
19.>>> greeter = print_call(greeter)
21.Calling greeter with arguments:
24.greeter returning 'Hi world!'
26.>>> greeter("Hi", what="Python")
27.Calling greeter with arguments:
30.greeter returning 'Hi Python!'
32.>>>So, this is at least mildly useful, but it'll get better! You may or may not have heard of closures, and you may have heard any of a large number of defenitions of what a closure is - I won't go into nitpicking, but just say that a closure is a block of code (for example a function) that captures (or closes over) non-local (free) variables. If this is all gibberish to you, you're probably in need of a CS refresher, but fear not - I'll show by example, and the concept is easy enough to understand: a function can reference variables that are defined in the function's enclosing scope.
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