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Sunday, March 16, 2014

Facts of python

  • Python is an interpreted language
  • In python, variables are never explicitly typed
  • Python doesn't let you reference a variable that has never been used
  • Lists are mutable and tuples are immutable
  • Python is object oriented. In python everything is an object in the sense that is can be assigned to a variable or passed as an argument to a function.
  • In python functions, modules, classes and individual instances of class are first-class-objects.
  • You can pass an entire module as an argument to a function
  • Python has no begin or end statement, no curly braces to say where the function (or any other code block) starts and where it end. The only delimiter is : ( def function_name () : ) and indentation
  • There are no subroutines in python. Everything is a function and all the functions return a value even if it is 'None'.
  • Function is also an object
  • All the functions start with 'def' 
  • Python functions doesn't define a return datatype. Python functions so not specify the datatype of their return value ; they don't even specify whether they return a value. In fact, every python function returns a value ; if the function ever executes a return statement, it will return that value ; otherwise, it will return None, the python null value.
  • Python keeps track of the datatype internally
  • The docstring (what ever is between """ and the next """ ) is available as an attribute of the function at runtime (.__doc__)
  • __name__ will give you the module name (actually the file name) without the directory path. By default, it is __main__ . If you do "import os ; print(os.__name__)" , you'll get "os" as the output
  • Python searches the directories defined in sys.path when you try to import a module. You can make it search a new path by using sys.path.insert(0, <new_path>)
  • Python uses try...except blocks to handle exceptions and raise statement to generate exceptions
  • The Boolean value for an empty tuple/list is false.
  • sets are unique bag of values. Example: a_set={1,2,3}. If you try to add a duplicate value to a set, it is ignored and you wouldn't even get an error.

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