Functions in Python
- 2. What is a function in Python? • Is a group of related statements that perform a specific task • Help break our program into smaller and modular chunks • As program grows larger and larger, functions make it more organized and manageable • Furthermore, it avoids repetition and makes code reusable
- 4. Example of a function
- 5. Docstring
- 7. How Function works in Python?
- 8. Scope and Lifetime of variables • Scope of a variable is the portion of a program where the variable is recognized • Parameters and variables defined inside a function is not visible from outside. Hence, they have a local scope. • Lifetime of a variable is the period throughout which the variable exits in the memory. • The lifetime of variables inside a function is as long as the function executes. • They are destroyed once we return from the function. Hence, a function does not remember the value of a variable from its previous calls.
- 9. Example
- 10. Types of Functions • Can be divided into the following two types: – Built-in functions: Functions that are built into Python – User-defined functions: Functions defined by the users themselves
- 11. Arguments
- 15. Python Recursion • What is recursion in Python? • Python Recursive Function • Advantages of Recursion • Disadvantages of Recursion
- 16. What is recursion in Python? • Recursion is the process of defining something in terms of itself • A physical world example would be to place two parallel mirrors facing each other • Any object in between them would be reflected recursively
- 19. Advantages of Recursion • Make the code look clean and elegant • A complex task can be broken down into simpler sub-problems using recursion
- 20. Disadvantages of Recursion • Sometimes the logic behind recursion is hard to follow through • Recursive calls are expensive (inefficient) as they take up a lot of memory and time • Recursive functions are hard to debug
- 21. Python Anonymous/Lambda Function • What are lambda functions in Python? • How to use lambda Functions in Python? – Syntax of Lambda Function in python – Example of Lambda Function in python – Use of Lambda Function in python
- 22. What are lambda functions in Python? • In Python, anonymous function is a function that is defined without a name. • While normal functions are defined using the def keyword, in Python anonymous functions are defined using the lambda keyword. • Hence, anonymous functions are also called lambda functions.
- 23. How to use lambda Functions in Python? • Syntax of Lambda Function in python
- 24. Example of Lambda Function in python
- 25. Use of Lambda Function in python
- 27. Python Global, Local and Nonlocal variables • Global Variables in Python • Local Variables in Python • Global and Local Variables Together • Nonlocal Variables in Python
- 28. Global Variables in Python
- 30. Local Variables in Python
- 31. Global and Local Variables Together
- 33. Nonlocal Variables in Python
- 34. Python Global Keyword • Python global Keyword – Rules of global Keyword – Use of global Keyword (With Example) • Global Variables Across Python Modules • Global in Nested Functions in Python
- 35. Python global Keyword • The basic rules for global keyword in Python are: – When we create a variable inside a function, it’s local by default – When we define a variable outside of a function, it’s global by default. We don’t have to use global keyword. – We use global keyword to read and write a global variable inside a function. – Use of global keyword outside a function has no effect
- 39. Global Variables Across Python Modules
- 41. Global in Nested Functions
- 42. Python Modules • What are modules in Python? • How to import modules in Python? – Python import statement – Import with renaming – Python from...import statement – Import all names • Python Module Search Path • Reloading a module • The dir() built-in function
- 43. What are modules in Python? • File containing Python statements and definitions – Example: example.py, is called a module • Use to break down large programs into small manageable and organized files. • Provide reusability of code • Can define our most used functions in a module and import it, instead of copying their definitions into different programs
- 44. How to import modules in Python? • Python import statement • Import with renaming • Python from...import statement • Import all names
- 48. Import all names
- 49. Python Module Search Path • While importing a module, Python looks at several places. • Interpreter first looks for a built-in module then (if not found) into a list of directories defined in sys.path. • The search is in this order. – The current directory. – PYTHONPATH (an environment variable with a list of directory). – The installation-dependent default directory.
- 52. The dir() built-in function • We can use the dir() function to find out names that are defined inside a module.
- 54. Python Package • What are packages? • Importing module from a package
- 55. What are packages? • We don't usually store all of our files in our computer in the same location. • Similar files are kept in the same directory, for example, we may keep all the songs in the "music" directory. • Analogous to this, Python has packages for directories and modules for files.
- 56. • As our application program grows larger in size with a lot of modules, we place similar modules in one package and different modules in different packages. • Similar, as a directory can contain sub-directories and files, a Python package can have sub- packages and modules. • A directory must contain a file named __init__.py in order for Python to consider it as a package. • This file can be left empty but we generally place the initialization code for that package in this file
- 58. Importing module from a package • We can import modules from packages using the dot (.) operator. • For example, if we want to import the start module in the above example, it is done as follows. – import Game.Level.start • Now if this module contains a function named select_difficulty(), we must use the full name to reference it. – Game.Level.start.select_difficulty(2)
- 59. • We can also import the module without the package prefix as follows – from Game.Level import start • We can now call the function simply as follows. – start.select_difficulty(2)
- 60. • Yet another way of importing just the required function (or class or variable) form a module within a package would be as follows. – from Game.Level.start import select_difficulty • Now we can directly call this function. – select_difficulty(2)
- 61. Thank You !