diff options
Diffstat (limited to 'python.html.markdown')
| -rw-r--r-- | python.html.markdown | 84 |
1 files changed, 61 insertions, 23 deletions
diff --git a/python.html.markdown b/python.html.markdown index d9eda60c..326ddb95 100644 --- a/python.html.markdown +++ b/python.html.markdown @@ -685,8 +685,8 @@ print(math.sqrt(16)) # => 4.0 # You can get specific functions from a module from math import ceil, floor -print(ceil(3.7)) # => 4.0 -print(floor(3.7)) # => 3.0 +print(ceil(3.7)) # => 4 +print(floor(3.7)) # => 3 # You can import all functions from a module. # Warning: this is not recommended @@ -733,7 +733,9 @@ class Human: self.name = name # Initialize property - self._age = 0 + self._age = 0 # the leading underscore indicates the "age" property is + # intended to be used internally + # do not rely on this to be enforced: it's a hint to other devs # An instance method. All methods take "self" as the first argument def say(self, msg): @@ -876,7 +878,8 @@ if __name__ == '__main__': if type(sup) is Superhero: print('I am a superhero') - # Get the Method Resolution search Order used by both getattr() and super() + # Get the "Method Resolution Order" used by both getattr() and super() + # (the order in which classes are searched for an attribute or method) # This attribute is dynamic and can be updated print(Superhero.__mro__) # => (<class '__main__.Superhero'>, # => <class 'human.Human'>, <class 'object'>) @@ -958,8 +961,7 @@ class Batman(Superhero, Bat): if __name__ == '__main__': sup = Batman() - # Get the Method Resolution search Order used by both getattr() and super(). - # This attribute is dynamic and can be updated + # The Method Resolution Order print(Batman.__mro__) # => (<class '__main__.Batman'>, # => <class 'superhero.Superhero'>, # => <class 'human.Human'>, @@ -1016,31 +1018,67 @@ gen_to_list = list(values) print(gen_to_list) # => [-1, -2, -3, -4, -5] -# Decorators -# In this example `beg` wraps `say`. If say_please is True then it -# will change the returned message. -from functools import wraps +# Decorators are a form of syntactic sugar. +# They make code easier to read while accomplishing clunky syntax. +# Wrappers are one type of decorator. +# They're really useful for adding logging to existing functions without needing to modify them. -def beg(target_function): - @wraps(target_function) +def log_function(func): def wrapper(*args, **kwargs): - msg, say_please = target_function(*args, **kwargs) - if say_please: - return "{} {}".format(msg, "Please! I am poor :(") - return msg - + print("Entering function", func.__name__) + result = func(*args, **kwargs) + print("Exiting function", func.__name__) + return result return wrapper +@log_function # equivalent: +def my_function(x,y): # def my_function(x,y): + return x+y # return x+y + # my_function = log_function(my_function) +# The decorator @log_function tells us as we begin reading the function definition +# for my_function that this function will be wrapped with log_function. +# When function definitions are long, it can be hard to parse the non-decorated +# assignment at the end of the definition. + +my_function(1,2) # => "Entering function my_function" + # => "3" + # => "Exiting function my_function" + +# But there's a problem. +# What happens if we try to get some information about my_function? + +print(my_function.__name__) # => 'wrapper' +print(my_function.__code__.co_argcount) # => 0. The argcount is 0 because both arguments in wrapper()'s signature are optional. + +# Because our decorator is equivalent to my_function = log_function(my_function) +# we've replaced information about my_function with information from wrapper + +# Fix this using functools + +from functools import wraps + +def log_function(func): + @wraps(func) # this ensures docstring, function name, arguments list, etc. are all copied + # to the wrapped function - instead of being replaced with wrapper's info + def wrapper(*args, **kwargs): + print("Entering function", func.__name__) + result = func(*args, **kwargs) + print("Exiting function", func.__name__) + return result + return wrapper -@beg -def say(say_please=False): - msg = "Can you buy me a beer?" - return msg, say_please +@log_function +def my_function(x,y): + return x+y + +my_function(1,2) # => "Entering function my_function" + # => "3" + # => "Exiting function my_function" +print(my_function.__name__) # => 'my_function' +print(my_function.__code__.co_argcount) # => 2 -print(say()) # Can you buy me a beer? -print(say(say_please=True)) # Can you buy me a beer? Please! I am poor :( ``` ### Free Online |