readme.md

Foreword

I'm not going to reinvent the wheel so this introduction to Python will be based on already existing and great tutorials available on web. At the beginning I have to also emphasise that some concepts and ideas are explained more on offline workshops by me, so just keep in mind that content available here is more of a reminder than a learning material per se. This introduction is (without bigger changes) bases on this introduction to Python3.

And so, without further ado, let's begin!

Introduction

Python was created by Guido Van Rossum in the early 90s. It is now one of the most popular languages in existence, and definitely one of the most fun to code in. We will go through fundamentals and try to solve exercises as we progress through.

1. Primitive Datatypes and Operators
2. Variables and Collections
3. Control Flow and Iterables
4. Functions
5. Modules
6. Classes
7. Advanced

Exercises

Exercises are in order that should represent progress of each section. You can read modules first and then try to solve exercises, or the other way. It's up to you. Just keep in mind that not always everything covered by modules will be sufficient to solve problems listed below. Extra sections are short exercises that relate to problem but try to emphasise some key concepts that might be overlooked at first sight.

1. Factorial

Because each and every programmer loves when things get big really fast. It's time to do so.

1. Write rec_factorial function using simple recursion.
2. Write iter_factorial function using while or for loop.
3. Write list_factorial function that will return list of first n factorials inclusive

Extra:

1. Try to break your code by passing an invalid value to functions. What happens, and why? What can you do to avoid this kind of errors?
2. Well, factorial of 5 is only 3 digits wide, how about 100 factorial? There should be an overflow, shouldn't it? Just like in C or Java. What happens?
3. list_factorial can be written in at least two ways. Which one is more efficient and why?
4. It is possible to write write factorial function in recursive form but using accumulator. Try to write acc_factorial

2. Fibonacci

What about all time favourite programming assignment? Let's see how difficult it will be using Python.

1. Write rec_fibonacci(n) function using simple recursion.
2. Write acc_fibonacci(n) function using recursion with accumulator.
3. Write iter_fibonacci(n) function using while or for loop.
4. Write list_fibonacci(n) function that will return list of first n fibonacci numbers inclusive.

Extra:

1. Try to break your code by passing an invalid value. Did you implement function in such way that it won't break when passed variable is string literal?
2. There is one other way to calculate fibonacci number. Can you implement it root_fibonacci? (hint: sqrt(5) ) Can you write another function to check for which n the difference between exact value and calcualted by this function is greater than some given delta?

3. Primes

What's not to love in prime numbers? I don't know either...

1. Write is_prime(n) function in best known way.
2. Write erastotenes(n) function that return list of only prime numbers from set of 0 to n (exclusive).

Extra:

1. Try to break your code. What about negative integers?
2. Look at range function and check if you can use its full potential in iterating over sequences by given step.
3. Look at map function. Write function only_primes([int]) that filters input list and returns list of only prime numbers from it.
4. There is a probabilistic way to check if number is prime. Try to implement Miller-Rabin primality test (miller_rabin_test).

4. Frequency counter

We all love books, don't we? Well if you don't, you should at least pretend to do so...

1. Write function most_used(file, count) that reads text file from input and returns list of count most used words from file and number of its occurrences. Let's assuble that we split text into words on whitespaces only. (hint: dictionaries and sorting lists might be useful)

Extra:

1. Can you write this code in fewer lines?
2. Using appropriate module you can define list of characters that will represent word separators (default .split() works on whitespaces). Modify your program so that words will be split on each character from defined list.

5. I'm terrible at remembering names...

Well, I probably won't remember yours... :(

1. Create dictionary friends where key == name && value == special_trade of all your friends.
2. Create list friend_names that only contains only names of your friends.
3. Create list special_trades that contains only those trades that no one else has.
4. Create new dictionary that is name: [trades].
5. Each person whom name starts with letter A gets new awesome trade.

Extra:

a = ["Awesome", "Awesomeness"]
b = [a for _ in range(3)]
b.append(["Awesome", "Awesomeness"])
a.append("End")
print(b)

6. First real homework

I know it's not mandatory course, but hey! I need to know if you understand anything so far. :)

# Dictionary that represents students from last class.
# Key: unique id, Value: (name, semester, list of favorite OS's) 
students = {
   0: ("Adam", 7, ["Linux", "Windows 10", "Mac OS"]),
   1: ("Konrad", 3, ["Linux"]),
   2: ("Monika", 3, ["Linux", "Windows"]),
   3: ("Piotrek", 3, ["Linux"]),
   4: ("Kuba", 3, ["Mac OS"]),
   5: ("Krzysiek", 3, ["Linux"]),
   6: ("Krzysiek", 3, ["Windows 10"]),
   7: ("Adam", 1, ["Windows 10"]),
   8: ("Marcel", 1, ["Windows 10"]),
   9: ("Paulina", 1, ["Windows 10"]),
   10: ("Sebastian", 1, ["Windows 10"])
}

1. Copy dictionary from above into your python file (module). I apologise if some data is incorrect, my memory is not perfect :)
2. Write function students_count(students) that returns number of students in class
3. write function was_present(students, name) that returns True only if someone of given name was on last class.
4. Write function unique_was_present(students, unique_id) that returns True only if someone of given unique_id was on last class.
5. Write function get_all_by_name(students, name) that returns sub-dictionary of students of given name.
6. Write function get_all_by_semester_range(students, sem_from, sem_to) that returns sub-dictionary of students that are on any semester starting from sem_from up to sem_to inclusive.
7. Write function how_many_use(students, os_name) that returns how many students use os_name operating system.
8. Write function get_all_names(students) that returns list of all the names of students.

7. Like a gentleman

With class...

1. Create Classroom class that has contains list of Students but has maximum number of students allowed (constructor parameter).
2. Each Student has unique id number, first and last name, and list of courses in current semester.
3. Add add_student, remove_student, has_student methods to Classroom class where argument is object of Student class.
4. Throw AlreadyInClassroomException exception if someone tries to add student of the same id as already in student list.
5. I know that I said list of Students but now I want to hold those objects in dictionary. (What should be used as key?)

class SomeClass(object):
    def __init__(self, a, b = 5, c = []):
        self.a = a
        self.b = b
        self.c = c      # This is mad!