functions.md

Functions

def function_name(vars...):
    body
    [return foo]

Lambdas

lambda parameters: expression

• single line only
• always expressions

Functions as arguments

• functions are first class citizens

def calc(operation, op1, op2):
    return operation(op1, op2)


print(calc(lambda a, b: a + b, 10, 5))

Closures

• access to variables in the enclosing scope is readonly

  def outer(msg):
      def inner():        # nested function
          print(msg)      # has access to msg (readonly)
      inner()
  
  outer("Hello")
  

• returning a function with closure

  def multiplier_of(n1):
      def mult(n2):
          return n1 * n2
      return mult
  
  multiplywith5 = multiplier_of(5)
  print(multiplywith5(9))
  

Decorators

• wrap a function into another functions
  • input checks, transactions, logging, ...
• @decorator_name

def auditable(old_function):
    def new_function(*args, **kwds):
        print("Calling %s" % old_function.__name__)
        return old_function(*args, **kwds)
    return new_function

@auditable
def foo():
    print("FOOOO")
    
foo()

Properties

• if setter is not defined, then the property is read-only

class Foo:
    def __init__(self):
        self._x = 0

    @property
    def x(self):
        print("getter")
        return self._x

    @x.setter
    def x(self, value):
        print("setter")
        self._x = value


f = Foo()
f.x = 1
print(f.x)