--Originally published at My B10g

A range in python is created with the function range(). To use this you must know it´s rules. First, if the range if not specified will begin at 0 and will reach the integer before the parameter given. For example:

for i in range(3):
...     print(i)
...
0
1
2

Second, in case you pass two parameter it will take it as beginning and end in that order, but again ending one integer before the end and increasing by one as before. For example:

for i in range(3, 6):
...     print(i)
...
3
4
5

Third, when you pass three parameters, it will proceed this way: beginning, end, steps. This will mean that it will move from the beginning the number of steps you entered until it reaches the closest one to the end. For example:

for i in range(4, 10, 2):
...     print(i)
...
4
6
8

Note: In this function you can use any integer positive or negative but you can’t use floats.

http://giphy.com/gifs/SurZxNuuGJl96

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Hacker tip:

if you want to use floats you can use this function:

def frange(start, stop, step):
...     i = start
...     while i < stop:
...         yield i
...         i += step

Shhhhhh don’t tell anyone.

You can see the original here:http://pythoncentral.io/pythons-range-function-explained/

It isn’t a well kept secret.

--Originally published at My B10g

When reading or writing a text file in python you can use the built in library of python to do so. The first step is to open the file and assign it to a variable for practical use (when you open a file you must define what you will be doing with it and to do so you need to use “r” for reading, “w” for writing, “a” appending or “r+”for reading and writing  ) . example:

file = open("hola.txt", 'r')

this mean I want to read file hola.txt

but to get what is in the file you can use:

file.read()

(to read all the file)

file.read(5)

(to read the first 5 characters)

file.readline()

(to read a complete line)

file.readlines()

(to read a list of strings of all the lines in the file)

To write in the file:

file.write("String")

(to write a string in a file)

file.writelines(variable)

(to write a list of strings separated by lines in the file )

When you do it this way you have to close the file at the end to optimize the program:

file.close()

But there are other ways to do it

using (with) there is no need to close the file.

with open("hello.txt", "w") as file:
	file.write("Hello World")

and you can do exactly the same things but writing less code.

--Originally published at My B10g

Most of the times that you create a program you expect it to interact with the user, and by doing so they may be doing things that they aren’t supposed to, like writing word where they should write numbers or use special characters in strings, in this cases the computer will drop an error and will stop the program but how to prevent it from stoping and just let the user know he is doing something wrong? that is exactly what this topic is about.

As in many things in programing how you do it depends on the programer and there are plenty of ways to do so, so I will be explaining just the basic concept and to do so I will use an example.

def get_int(prompt):
    try:
        value = int(input(prompt))
    except ValueError:
        print("Sorry, I didn't understand that.")
        return get_int(prompt)

    if value < 0:
        print("Sorry, your response must not be negative.")
        return get_int(prompt)
    else:
        return value

to get started we need to know that we will need to create a loop (in this case the loop is created by calling the function again once it finds a mistake) because you want it to no matter how many times the user make a mistake the program should not stop until everything is correct, next we will need to check if the input is the correct type, to do so we will transform the input to an integer and in case it isn’t a number it would drop a mistake and for that we will use an except which will execute what should it do in case the program find a mistake of this type, in this

--Originally published at My B10g

Tuples:

tuples gather information all together but you cannot change it´s order or add and remove things in it, to make a tuple it only requires a name and the use of () parenthesis.

example:

months = ('January','February','March','April','May','June',\
'July','August','September','October','November','  December')
print(months)

Note: you can use “\” to jump a line and organize it better

Lists:

List also save data but in the case of lists you can reorganize the values and add more  using List_name.append(‘added value’), you can also erase values using del List_name[#].

example:

cats = ['Tom', 'Snappy', 'Kitty', 'Jessie', 'Chester']

print (cats[2])

cats.append('Catherine')

del cats[1]

print (cats)

more at: http://sthurlow.com/python/lesson06/

Poem of the day:

--Originally published at My B10g

Types of repetition

The while loop: for indefinite number of repetitions(use more cpu)

The for loop: for an specific number of repetitions

Nested loops – loops within loops: run a process which run other process and the first process will not run again until the nestes process finished running

The recursion: repeats until it gets to one case which doesn’t call itself, used to reduce coding.

more interesting stuff in: http://www.annedawson.net/Python3_Repetition_StringFormatting.htm

beautiful poem of the day

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