Hey guys, Hope you all are doing great.

I have always found Regular expressions or REGEX quite amazing. You can solve your string related problem in just some simple magic of patterns.
Our brain works very well to identify the pattern in our day to day life. As these are visual clues, we tend to catch and analyse them better. In fact, their you make negligible mistake to tackle the scenario.
Say you have a pattern with concentric cirles:


Now you see that it has got a pattern in here, the small circle grows by some radius say x and we have another circle and so on...
This can be generalized in mathematical way, as in geometry is:
x + y + 2gx + 2fy + c' = 0
This same thing applies to string patterns or character arrays.
For Python we have a Regex module called re

 Below are few function which you will find useful is many applications 

Syntax Definition Examples
re.search(regex,str) return match object if found, else None 
pika = re.search(r"\w+@\w+\.com", "from pikachu@pokemon.com address")

if pika :
    print "yes"
    print pika.group() # → pika@pika.com
else:
    print "no"
re.match(regex,str) similar to re.search(), but match starts at beginning of string. 

goku = re.match('ha','kamehameha') # succeed

if goku == None:
    print "no match"
else:
    print "yes match"
re.split(regex,str) return a list. 

print re.split(r' +', 'Clark   Kent  is Superman')'
# output: ['Clark', 'Kent', 'is', 'Superman']

print re.split(r'( +)(@+)', 'what   @@do  @@you @@think')
# output: ['what', '   ', '@@', 'do', '  ', '@@', 'you', ' ', '@@', 'think']

print re.split(r' ', 'a b c d e', maxsplit = 2)
# output: ['a', 'b', 'c d e']
re.findall(regex,str) return a list of non-overlapping (repeated) matches. 

print re.findall(r'( +)(@+)', 'what   @@@do  @@you @think')
# output: [('   ', '@@@'), ('  ', '@@'), (' ', '@')]
re.finditer(…) similar to re.findall(), but returns a iterator. 

for matched in re.finditer(r'(\w+)', 'where   are  the avengers'):
    print matched.group()       # prints each word in a line
re.sub(regex,replacement,str) does replacement. Returns the new string. 

def ff(pika):
    if pika.group(0) == "bulba":
        return "vena"
    elif pika.group(0) == "mender":
        return "izard"
    else:
        return pika.group(0)

print re.sub(r"[aeiou]+", ff, "bulbasaur") # venasaur
print re.sub(r"[aeiou]+", ff, "charmender") # charizard
print re.sub(r"[aeiou]+", ff, "geek") # geek
re.subn(…) similar to re.sub(), but returns a tuple. 1st element is the new string, 2nd is number of replacement. 

re.subn('\w+', 'Try', 'Cry Cry, Cry and Cry Again!', count=3)
# ('Try Try, Try and Try Again!', 3)
re.escape(str) add backslash to string for feeding it to regex as pattern. Return the new string. 

re.escape('Lets meet spider man?')
# output: Lets\\ meet\\ spider\\ man\\?

To form a regular expression, it needs a bit or creativity and foresightedness of the outcome.
For sure you need to know the regex symbols and rules to do that, and all should be dancing in your mind to create an efficient and effective pattern. To help you out, below is the Python Regex Jump-starter:
Python Regex Jump-starter:
Regular Expression Basics
. Any character except newline
a The character a
ab The string ab
a|b a or b
a* 0 or more a's
\ Escapes a special character
Regular Expression Quantifiers
* 0 or more
+ 1 or more
? 0 or 1
{2} Exactly 2
{2, 5} Between 2 and 5
{2,} 2 or more
(,5} Up to 5
Default is greedy. Append ? for reluctant.
Regular Expression Groups
(...) Capturing group
(?P...) Capturing group named Y
(?:...) Non-capturing group
\Y Match the Y'th captured group
(?P=Y) Match the named group Y
(?#...) Comment
Regular Expression Character Classes
[ab-d] One character of: a, b, c, d
[^ab-d] One character except: a, b, c, d
[\b] Backspace character
\d One digit
\D One non-digit
\s One whitespace
\S One non-whitespace
\w One word character
\W One non-word character
Regular Expression Assertions
^ Start of string
\A Start of string, ignores m flag
$ End of string
\Z End of string, ignores m flag
\b Word boundary
\B Non-word boundary
(?=...) Positive lookahead
(?!...) Negative lookahead
(?<=...) Positive lookbehind
(?<!...) Negative lookbehind
(?()|) Conditional
Regular Expression Flags
i Ignore case
m ^ and $ match start and end of line
s . matches newline as well
x Allow spaces and comments
L Locale character classes
u Unicode character classes
(?iLmsux) Set flags within regex
Regular Expression Special Characters
\n Newline
\r Carriage return
\t Tab
\YYY Octal character YYY
\xYY Hexadecimal character YY
Regular Expression Replacement
\g<0></0> Insert entire match
\g Insert match Y (name or number)
\Y Insert group numbered Y

 Please let me know your feedback, on how i can improve and make it better. Till then!! Cheers!!
Posted by
1

View comments

Greetings!! Here's a series of Cold Golf problems and solutions in Python as a part of 21 days of Code | Code Golf by Skillenza 

https://skillenza.com/challenge/21days-of-code

DAY - I

A Little Complex

Given n complex numbers each x + yi, where x is the real part and y is the imaginary part, find their product.

Input Format

The first line of input consists of an integer t denoting the number of test cases. t test cases follow.
1

For the need of a simple tabular Grid in your Angular JS application, one of the most basic and simple to use package is angular-ui-grid. The implementation is easy in many of the use cases, but when it comes to extend the limits of the ui-grid, life becomes tough.

One of the tricky task is to set the Grid height as dynamic, in other words to make the grid more flexible to number of rows and the grid size would depend on it.

Hey guys, Hope you all are doing great. 

Algorithm To Convert Post-fix Expression into Infix expression:-

Scan the Post-fix String from Left to Right. If the character is an Operand, then Push it on to the deque. If the character is an Operator, then Pop left Operator 1 and Operand 2 and concatenate them using Infix notation where the Operator is in between the Two Operands. The resultant expression is then pushed on the deque.

Hey guys, Hope you all are doing great.

As the first part of this series of Python package and installation we will cover pip vs Conda

pip vs Conda

pip

Python packages only. Compiles everything from source. Installs binary, wheel, the ones which pypi supply Blessed by the core Python community (i.e., Python 3.4+ includes code that automatically boostraps pip). conda

Python agnostic.

Hey guys,

Hope you all are doing great. I love Code Golfing, what it brings out in you is the hidden concepts of a programming language and especially the push to implement same thing in numerous ways.

Code Golfing and Python - Yeah that's my Poison!

Below are few tips and tricks which will give you an edge over other programmer to write the shortest code:

1. The foo if condition else bar condition can be shortened to

True if condition else False ------- [False,True][condition]

2.

Hey guys, Hope you all are doing great.

I have always found Regular expressions or REGEX quite amazing. You can solve your string related problem in just some simple magic of patterns.

Our brain works very well to identify the pattern in our day to day life. As these are visual clues, we tend to catch and analyse them better. In fact, their you make negligible mistake to tackle the scenario.
1

Hey guys, Hope you all are doing great. I am back with Some Python Programming tips for

CODE GOLF Challenges.

Here are the Second part of code golfing Tips in Python

I prefer Python or Python3 myself for code golfing

So we will discuss dome tips as generics for code golf programming in Python:

7. Use `n` to convert an integer to a string instead of using str(n).

Hey guys, Hope you all are doing great. I am back with Some Python Programming tips for

CODE GOLF Challenges.

So, What is CODE GOLF??

As per Wikipedia, it is a type of recreational computer programming competition in which participants strive to achieve the shortest possible source code (not to be confused with binary Sizecoding) that implements a certain algorithm.
12

Hey guys, Hope you all are doing great. I am back with with a byte of python performance.

I have been playing on codingame.com a lot now a days during my weekends.

Its cool site for the player aka coders who want to try there hands into gaming domain.
Loading