Hello dear friends, God bless Venezuela.  

For  some months I've talked about creating a database with Python Dictionary and some TXT, and you can really! It's very interesting to be  able to use the Power of the dictionary as a database.

But why use a Python Dictionary as a Database?

Dictionaries have the feature that they are stored directly in RAM which makes any call with their methods almost instantaneous.

The structure of the Python variables is interesting, for example we have:  

• Chains  
• Lists  
• Tuples  
• Dictionaries  

Chains, Lists and Tuples, share many common methods, but they have their differences, for example: 

• One string can be seen as a list of characters.
• Lists can contain strings, Tuples and even dictionaries and are mutable that is to say they can change.
• While  the Tuples are very similar to the Lists they share their methods but  they can not change, they are defined and they are that way, but they  are very interesting because they weigh much less than a list.

The dictionaries for me are another level in programming with Python,  it's like doing magic, creating dictionaries that really work as we  want.  

Today  we are going to see some examples of code that I have used in my  programs, I have always used a simple code to add data as if it were a  Database with my Dictionary in a TXT, I charge it and it works very fast  and it is re-usable.  

I'm talking about my letter counter, I remember when I had to do it in  Coursera in the specialization and now I see how much it has helped me  until today.  

This  time we are going to add a file that stores all the entries that we  pass and keeps the repetition of the letters, so we can add and add data  and function as a Pythonica database, here the code:

file = open("BD_count_letter.txt")

data = file.readline()

dict_charts = data.strip()

dict_charts = eval(dict_charts)

if dict_charts != "":

    dict_charts = eval(dict_charts)

else: 

    dict_charts = {}

string = raw_input("WRITE A CHARACTER CHAIN:")

for character in string:

        if character not in dict_charts:

                  dict_charts[character] = 1

        else:

                  dict_charts[character] = dict_charts[character] +1

print dict_charts

file = open("BD_count_letter.txt", "w")

file.write(str(dict_charts))

file.close ()

Let's review the code:

file = open("BD_count_letter.txt")

data = file.readline()

First we open a name file: file = open("BD_count_letter.txt") can have any name, but I put that, must be created eye.

Next we go to read the file and eliminate the lines and blank spaces on both sides of the chain:

dict_charts = data.strip()

dict_charts = eval(dict_charts)

Now we evaluate the data that we bring from the files and ask for a chain to add to the dictionary of our database.

The Conditional is to know if the Dictionary is in the TXT otherwise we have to create it!

if dict_charts != "":

    dict_charts = eval(dict_charts)

else: 

    dict_charts = {}

Now we need to  combine the dictionary with the string, this we do with a for, every  time we find a letter that does not exist in the dictionary the loop  will send it to add it:

string = raw_input("WRITE A CHARACTER CHAIN:")

for character in string:

        if character not in dict_charts:

                  dict_charts[character] = 1

We enter the  loop, and we have a conditional, this verifies "if the letter exists" in  the dictionary adds 1 to the times that existed already.

        else:

                  dict_charts[character] = dict_charts[character] +1

Once the cycle is finished, the dictionary is printed if it is desired to verify the output:

print dict_charts

Now we proceed to open the File in writing mode and add the new dictionary that is just the same with the changes.

file = open("BD_count_letter.txt", "w")

file.write(str(dict_charts))

file.close ()

We  already know what works now it's your turn to try it, and wait for the  next post where I'll tell you where I'm using this simple code that  helps me in many programs. We'll also see other options to format those  ugly symbols and we'll make some very interesting graphics of Cloud.

Que Dios Bendiga a Venezuela, hasta la Próxima.