Python Lists

Today I will show you some very interesting methods that can be used in Python lists, which can often save your time.

Most methods can be found in the following link: https://docs.python.org/2/tutorial/datastructures.html

Create a characters list:

lista = ['1', '4', '3', '2', '5', '7', '6', '8', '9']

Convert all characters of the list to int:

lista = map(int, lista)

Show the greatest value from the list:

print max(lista)

Show the lowest value from the list:

print min(lista)

Sum all values from the list

print sum(lista)

Search and returns the index of the value passed by parameter:

lista.index(7)

Sort the list in ascending order:

lista.sort()

Reverse the list

lista.reverse()

Insert all elements of a list at the end of another list:

lista.extend(lista2)

Remove the value passed as parameter (the first found in the list):

lista.remove(14)

Remove the last value from the list:

lista.pop()

Remove the first value from the list:

lista.pop(0)

Count how many times the parameter appear in the list:

lista.count(3)

Convert a string into a list:

lista = []

string = '1 2 3 4 5 6 7 8'

lista = string.split()

Transform a list into a string (separate by comma):

lista = ['1', '4', '3', '2', '5', '7', '6', '8', '9']

string = ', '.join(lista)

print string

Generate a random value from the list:

import random

random.choice(lista)

These are some methods you can use in your algorithm when you are working with lists in Python. 
I hope you enjoyed the tips.

Tower of Hanoi - Python

Today i will show a little example in Python of the famous problem Tower of Hanoi.

"The Tower of Hanoi is a mathematical game or puzzle. It consists of three rods, and a number of disks of different sizes which can slide onto any rod. The puzzle starts with the disks in a neat stack in ascending order of size on one rod, the smallest at the top, thus making a conical shape.

The objective of the puzzle is to move the entire stack to another rod, obeying the following simple rules:

1. Only one disk can be moved at a time.
2. Each move consists of taking the upper disk from one of the stacks and placing it on top of another stack i.e. a disk can only be moved if it is the uppermost disk on a stack.
3. No disk may be placed on top of a smaller disk.

With three disks, the puzzle can be solved in seven moves. The minimum number of moves required to solve a Tower of Hanoi puzzle is 2ⁿ - 1, where n is the number of disks." 

See the example below:

If you want to know more about Tower of Hanoi click here

Ok, ok, but where's the code?

1 2 3 4 5 6 7 8 9 10

def Hanoi(pin0, pin2, pin1, num): if num == 1: print 'Move from ' + str(pin0) + ' to ' + str(pin2) else: Hanoi(pin0, pin1, pin2, num-1) Hanoi(pin0, pin2, pin1, 1) Hanoi(pin1, pin2, pin0, num-1) # Parameters: (from)Pin0, (to)Pin2, (helper)Pin1, Number of Disks Hanoi(0, 2, 1, 3)

The code shows each necessary move to pass all the disks from the first rod to the last rod.

If you liked please share. If you have any questions just ask.