Here are my Project Euler solutions in Python. The purpouse of the project is to try the Python language... Why is Python so popular? I do not know. But I wanna find out for myself. I decided to take the Project Euler problems and try to learn Python when solving them. Project Euler was hacked recently so they do not allow to check the solutions. After they will fix the site I will fix potential issues in the commited code. I have already solved around 70 of the problems few years back so solving them once more time should be easier. Usually I develop stuff in Java and I also like Ruby language. Im trying this on my notebook, it has W8.1. I am developing in Sublime Text and compiling using Python 3. I did not use Python before this project. I heard about Python before and saw some code.
Ok, I choosed Python 3 as its said on the pages that Python 2 is legacy. It is strange that python executable has diffent mode when you run it without arguments and when you run it to run a program. It took me some time to figure this out. I set up the Python3 build system, Python needed to be in path for it to work. Now I press ctrl+b and I see output of the Python program.
Problem one is easy one. I learned how to create function, how to do a simple for cycle, if statement and printing. Day 2
Problem two is easy as well. Nothing to think about here, simple cycle will do. I learned how to do while cycle. Day 3
Finaly some playing with primes in problem three. As I remember from few years back, there will be a lot of prime problems ahead of me, so I created the Sieve of Eratosthenes function. It probably is somewhere in Python ecosystem already, but I am not that far yet. This is the first time I used import to successfully import math module. I learned how to print last element of array. Day 4
Ok, so I will need the sieve I created on Day 3 again. Time to create my own module. It took me some time to find out how exactly call the methods from my imported module. At the end it is of course trivial - name_of_module.name_of_method. I will leave the old code in problem3.py for historical purposes even though it should be refactored. It is also the first time i am working with set. The solution of the fifth problem that I have chosen could be probably improved, but I am not here for the perfection. Day 6
This problem probably wants us to finally create the sieve. I already have it, so again easy solution not much to learn here. Day 8
I decided to version the progress. I created github repository and put the code inside. In problem eight I was practicing how to work with characters of a string and convert string to integer. To be honest I do not like the global methods - len, str, int. I am used to have this methods on my objects from ruby - size/lenght is attribute of an object why is len a global function?
Day 9
I had a chance to sort an array in Python when solving problem nine. I was again surprised that the sorted method flies in the air in global namespace. From the list of build in functions I also learned that the range function that I used in the for cycles is also a global function. It is obvious of course.
Day 10
I have learned how to initialize array of arrays. Also I learned that Python does not like number 04. Day 12
I decided to create the diary because I learned a lot today. The notes from before this one are aproximations of what I remember.
I found out that just simple counting factors is not enought for problem twelve. So I created another method that is returning dictionary structure that contains full factorization of a number. I discovered how to raise an Error when debuging the method. I was also playing with the map function but decided to give up for now and return to it later. I refactored the primes library to store the calculated sieve in cache variable. I found out that two leading underscores should make a variable private inside a module. I needed to refactor problem5.py so that it is still runable. Day 13
Problem thirteen is targeting languages where integers can easily overflow. Python is not such a language. I learned that summing an array can be done using the global function sum.
Day 14
Today I learned how to use the ternary if else operator in Python. Somehow I find it strange that the same operator does not seem to work without the else part. I would enjoy writing return x if condition when handling special cases. I also read about how to write the ternary operator in old Python - (lambda a, lambda b)[a>b]. Today I also used Python syntax for my benefit for the first time when debuging the solution. Deciding between printing intermediate solutions or printing just a final solution was just moving the printing code with tabs back and forth.
Day 15
Today I learned how to initialize matrix with zeros on all lines - [[0]*matrix_size]*matrix_size will have the same value in all elements. Instead I had to use matrix = [[0 for i in range(0,matrix_size)] for i in range(0,matrix_size)]. The project euler site now checks for solutions again. I found a bug in few problems and learned few new things among the way to fix those. I learned how to merge dictionaries. Using lambda got to me easier than when I used it last time and I learned a little bit about commenting python code.
Day 16
Problem sixteen is my first one liner solution. I studied more the iterable object that you get from for cycle.
Day 17
Today I had much more fun with lambda method than the last time. After learning how to read from file, I mapped the input file into list of lists of integers.
Day 19
Today I learned that if you want to add element to a list, you need to use append method, if you will try to append list to a list append method will add the whole list as 1 element. You need to use extend method to add all elements of another list to your list. If you want to add something to a set, no matter if 1 element or set of elements, you need to use the update method. Let me see how long it will take until I will remember this. Day 22
I used the enumerate function today, read from file again, sorted a list. I learned how to convert character into its ascii number.
Day 23
Today I had the honor to meet the sys package for the first time. I tried writing to stdout and flushing the output. Day 24
I practiced a little bit with lists and stuff... Nothing to talk about really. Math problems will start to not be enough to progress my Python knowledge. Day 25
Today I learned how to open browser from Python. For opening problem 25 I created script to show me next problem that I did not work on yet. Day 26
This is what you do when you want to find positions of an element in a list: [i for i, x in enumerate(list) if x == element]
Day 27
So today I started feeling that 1 day will not be enough for 1 problem soon. Today I played with sets a little bit. I also learned about the functools.reduce() method. I like this functional approach.
Day 30
I had much less python related trouble solving the problem today. I am getting somehow used to the language. Day 31
Today I found out that I can write some of the lambda calls without much thinking. Also every line should end with a line terminator - new line. This is why python files should end with an empty line. Actually it is not ending with an empty line. File ends with an new line character. Day 35
Today I found out that range can be called with just one parameter... I learned about loop controlling statements in python.
Day 37
Today I learned something about documenting and the __doc__ special attribute. I tried to document the primes.py file.
Day 38
Today I sorted characters in a string. Not that I would find this usable in a real world application. Day 39
I was reading about the problems Python has on Windows (for instance here ). I did not manageed to get into situation where I would have any problems with python so far, but I did not install any modules yet. I will need to look into it more deeply. Day 41
Ok I think that I am pretty convinced that i can do some stuff using the basic Python so I guess from now on I will post here less often