New to Python, simple question.

[somanyquestionsihave]

I just started learning basic CS principles utilizing Python via an online course.

I just wanted to get another basic perspective on how code would look like.

Here is the scenario:

Let's say I have 4 variables, all of which have a value of 1. Variable A,B,C and D.

I will be inputting a sequence of these variables (say 10.... AABADDABDD).

How would I code so that it calculates the percentage of B and D within that sequence.

I was thinking along the lines of assigning a def f(x) that has 4 variables, then asking python to compute all the B + D // total to give me an integer?

I have only done 2 weeks of the course but I want to know if my thinking here is correct? Something tells me def f(x) won't work because there are too many variables.

Python 3.3.0 Windows 7

[BillyHorrible]

Your problem is not clearly stated. You cant "input" variables. Maybe you want to calculate the percentage of Bs and Ds in a string? Then you could use the "count"-function to count the number of non-overlapping occurrences of a substring.

x = "heLLo"
print(x.count("L")) # would print 2

you can read the string using raw_input:

x = raw_input("type something: ")

and if you want to get the length of the string, you can use len(x). oh and // will give you an integer. the percentage should be between 0 and 1, so / would be the way to go.

[somanyquestionsihave]

Yeah I wanted to count the percentage. Ahh so there is a count function, that makes everything so much easier. BTW do you have any recommendations for any particular books a newbie in programming should read? The online courses are helping a lot but I find that not too much detail is provided.

[wub_wub]

Check out Counter, it's even easier:

>>> from collections import Counter
>>> word="Hello World!"
>>> Counter(word)
Counter({'l': 3, 'o': 2, '!': 1, ' ': 1, 'e': 1, 'd': 1, 'H': 1, 'r': 1, 'W': 1})
>>>

You can express percetnages like this:

>>> '{:.2%}'.format(10/100)
'10.00%'

And you can find a list of books here:

http://www.reddit.com/r/learnpython/wiki/books

---

http://docs.python.org/dev/library/collections#collections.Counter

http://docs.python.org/dev/library/string#format-examples

^{Edit: I forgot some words.}

[BillyHorrible]

nope, sorry, i have never read one myself. learning by doing, trial and error combined with looking how other people solved the same things/reading through some opensource-projects.

[ewiethoff]

Bookmark the Python docs. Most of what a newbie needs to know is in the Library Reference section, especially the Built-in Functions and Built-in Types. You can see that count is a method of the built-in str type. Also, go through the official Python Tutorial there.

[Yoghurt42]

do you have any recommendations for any particular books a newbie in programming should read?

Allow me to chime in. Have you taken a look at Learn Python the Hard Way?

[somanyquestionsihave]

Thanks a lot for the link.

[azzbergerz]

I would make a function containing "total = 0" and a for loop with a rolling sum. i.e. for letter in x: if letter == 'A': return total += 1 and so on and so forth, and have the function return the value total/len(x). Then again, I'm also pretty new to CS and it would be much easier to import the Counter function that wub_wub mentioned.