Python learning: scrapbook

Apr 26, 2019 • Pradeep Pant

While browsing my Evernote I found a scrapbook which I have made while learning Python some years back. Thought to share if this helps someone. I am pasting directly (no editing so there might be some spell and grammar mistake).

Python 2 division, just use integer part (3/2=1) whereas Python 3 uses real division 3/2 = 1.5
Strings in Python are immutable means you can’t change the in-place value of a char. Once string is created you can’t change/replace its elements
s= “Hello World” s[::-1] this will reverse string s “dlroW olleH” double colon is used to tell the range and also how many elements can be skipped
if you want to use Python 3 functions in Python 2 then use ‘from __future__ import print_function‘ and similarly other functions
List are mutable but tuples are not mutable (does not support item assignment) aka immutable, fewer methods in tuples then why to use instead of a list? The key is immutability. in a program if you want sequence/Val does not to get changed then tuple is a solution e.g.; storing calendar dates which know will not change during your programs.
Set is a collection of un-ordered unique items it looks like a dictionary (in notation) but only keys which are unique. It can help in removing repeated items means you can use set to cast list.
List comprehensive are an excellent way to write clean and efficient code – they are actually de-constructed for loop flatted out in a list
Lambda expressions can be used to shorten function this is really useful when used with map(), reduce() and filter() functions
First class functions: Treat functions like any other object, we can pass functions, we can return functions, we can assign functions to a variable
Closure: Closure takes advantage of first-class functions and returns inner functions and variables local to them.
Decorators: It is a function which takes another function as an argument and returns as a function without changing the source code of the original function. Decorator allows easily to add functionality inside our wrapper without modifying original function.

Note: These are notes for quick reference. If you are serious in learning Python I encourage you to take a book or a tutorial.

Enjoy learning! More to come …