#!/usr/bin/env python # coding: utf-8 # ## Python Introduction with some detours # ![Python](https://www.python.org/static/community_logos/python-logo-generic.svg) # ![xkcd](https://imgs.xkcd.com/comics/python.png) # ## Python created by Guido von Rossum in early 1990s (later at Google,Dropbox) # ## Language reference: https://docs.python.org/3/index.html # # ![Guido](https://upload.wikimedia.org/wikipedia/en/thumb/d/d0/Guido-portrait-2014-curvves.jpg/435px-Guido-portrait-2014-curvves.jpg) # # Why Python? # ## Why Python but not Julia or R or some other language or even VBA in Excel? # ### Readability, Glue Language(APIs), From Startups to Google and Facebook, Pipeline # # Prime numbers in J language used at some finance institutions **1: I. 2= +/ 0= (] |/ ]) i.y** # ## Python is now programming language # 3 in TIOBE language index (as of September 2018) # https://www.tiobe.com/tiobe-index/ # # https://developers.slashdot.org/story/18/09/08/1722213/python-displaces-c-in-tiobe-index-top-3 # ![Anaconda](https://www.anaconda.com/wp-content/themes/anaconda/images/logo-dark.png) # https://www.anaconda.com/download/ # ### Jupyter Basics # # * Esc-M turns cell into Markdown cell for formatting (https://guides.github.com/pdfs/markdown-cheatsheet-online.pdf) # * Esc-Y turns cell into code cell(default) # # # * Ctrl-Enter runs code of cell in place # * Alt-Enter runs code for current cell and creates a new cell below # * Esc-A creates a new cell above current cell # * Esc-B creates a new cell below current cell # * Esc-dd deletes current cell # ## What is Programming? # # * Egg algorithm # * Computers are stupid, they only do what they are told to do # * If it is stupid but it works, then it is not stupid # * Make it work, make it right, make it fast(last two steps often not required in real life) # * GIGO principle # # * Error messages are nothing to be afraid of, usually the message will explain what needs fixing! # In[ ]: print("Hello World!") # In[ ]: # Our first comment # Real Program Comments should generally describe why # Here comments will describe extra information not covered or needed for starting out # REPL(Read,Eval,Print, Loop) # Python - Interpreted Language(commands executed as they come) # ## Most important Python ideas # * dir(myobject) to find what can be done (most decent text editors/IDEs will offer autocompletion and hints though) # * help(myobject) general help # * type(myobject) what type it is # # ## : indicates a new indentation level # ## id(object) # # Return the “identity” of an object. # # This is an integer which is guaranteed to be unique and constant for this object during its lifetime. # Two objects with non-overlapping lifetimes may have the same id() value. # # #### CPython implementation detail: This is the address of the object in memory. # In[ ]: myname="Valdis" # Creating our first variable will persist through this workbook once it is run # ## Strings # * immutable # In[5]: print(myname) #print is a function that takes at least one argument # 2.7 and older Python was print without parenthesis # In[ ]: favfood="potatoes" # ## "f-strings", “formatted string literals” # # In some other languages also known as string interpolation # In[ ]: print(f"My name is {myname} and my favorite food is {favfood} ") # f strings in Python 3.6+ older formatting methods not covered in this course # https://realpython.com/python-f-strings/ # ## What is a function? # * A function is a block of organized, reusable code that is used to perform a single, related action. # * Single, organized, related always ? :) # ### DRY - Do not Repeat Yourself principle # * Every piece of knowledge must have a single, unambiguous, authoritative representation within a system. http://wiki.c2.com/?DontRepeatYourself # # * Contrast WET - We Enjoy Typing, Write Everything Twice, Waste Everyone's Time # In[ ]: def printName(name): print(f"Maybe my name is: {name}") # In[ ]: printName("Voldemars") # In[ ]: #Functions can also return values def combinedName(name,last): return name+" "+last # In[ ]: fullname=combinedName("Valdis","Saulespurens") # In[ ]: sometext="It's a string which allows single quotes" anothertext='This string allows "double quotes" without escaping' longstring='''This is a multiline string Seriously long string with many lines lots of text covered''' # In[ ]: print(longstring) # In[ ]: ## Some strings might need escaping such as \\, \", \', \t # In[ ]: ## Everything in Python is an Object ## can use id(myobject) to find its identity - place in memory ## each object has a value with a type and can be mutable/immutable # # ### Data types in Python 3.x # # * Integers type(42) int # * Floating Point type(3.14) float # * Boolean type(True),type(False) bool # * String(ordered, immutable char sequence) type("OyCaramba") str # * List type([1,2,63,"aha","youcanmixtypeinsidelist", ["even","nest"]]) list # * Dictionary(key:value pairs) type({"foo":"bar", "favoriteday":"Friday"}) dict # * Tuple - ordered immutable sequence type("sup",7,"dwarves") tup # * Set (unordered collection of uniques) ("k","a","r","t","u","p","e","l","i","s") # In[ ]: # Variables a = 5 # Integer b = 5.6 # Float c = "sometext" # String print(type(a),type(b),type(c)) # In[ ]: a = "42" # now a is a String type(a) # notice how without print the output is a bit different # In[ ]: # Naming conventions # start with lowercase # _ between words or camelCase # style guide: https://www.python.org/dev/peps/pep-0008/ # ## Arithmetic Operators # ## + - * / # ## **(power) # ## % modulus # ## //(integer division) # # In[ ]: 5+4*3-(6/2) # In[ ]: 5//2 # In[ ]: 4%3 # In[ ]: type(1) # In[ ]: type(14.0) # In[ ]: 5**33 # In[ ]: 11**120 # no maximum anymore # ## Python Lists # # * Ordered # * Mutable(can change individual members!) # * Comma separated between brackets [1,3,2,5,6,2] # * Can have duplicates # * Can be nested # # In[ ]: # In[ ]: mylist = list(range(11,21,1)) # mylist = [11, 12, 13, 14, 15, 16, 17, 18, 19, 20] would work too but not practical for longer ranges... print(mylist) # ### Slice notation # # somestring[start:end:step] # # somelist[start:end:step] # # start is at index 0(first element), end is -1 the actual index # #### Examples below # In[ ]: mylist[0] # In[ ]: mylist[3:] # In[ ]: mylist[:-2] # In[ ]: mylist[::2] # In[ ]: "Valdis"[2:5] # In[ ]: myname[-1] # In[ ]: myname[::-1] # # ### Common list methods. # * list.append(elem) -- adds a single element to the end of the list. Common error: does not return the new list, just modifies the original. # * list.insert(index, elem) -- inserts the element at the given index, shifting elements to the right. # * list.extend(list2) adds the elements in list2 to the end of the list. Using + or += on a list is similar to using extend(). # * list.index(elem) -- searches for the given element from the start of the list and returns its index. Throws a ValueError if the element does not appear (use "in" to check without a ValueError). # * list.remove(elem) -- searches for the first instance of the given element and removes it (throws ValueError if not present) # * list.sort() -- sorts the list in place (does not return it). (The sorted() function shown later is preferred.) # * list.reverse() -- reverses the list in place (does not return it) # * list.pop(index)-- removes and returns the element at the given index. Returns the rightmost element if index is omitted (roughly the opposite of append()). # ## Dictionaries # # * Collection of Key - Value pairs # * also known as associative array # * unordered # * keys unique in one dictionary # * storing, extracting # In[ ]: mydict = {"country":"Latvia"} #Key-Value store, also knows as Hashmaps, Keys must be unique # In[ ]: mydict["food"]="potatoes" # In[ ]: mydict["food"] # In[ ]: mydict["country"] # In[ ]: mydict.keys() # In[ ]: mydict.values() # In[ ]: "potatoes" in mydict.values() # ## Sets # # * unordered # * uniques only # * curly braces {3, 6, 7} # In[ ]: s={3,3,6,1,3,6,7} print(s) # ## Tuples # # * ordered # * immutable (cannot be changed!) # * Can be used as a collection of fields # In[ ]: mytuple = 6, 4, 9 print(mytuple) # ## Conditional operators # ### < > <= >= == != and or not # In[ ]: if 5 >= 5: print("hello") if 5 <= 5: print("hello") if 5 == 6: print("hello thats magic") if 5 != 6: print("hello thats not magic") # In[ ]: def printnum(num): if num > 10: print(f"This number {num} is too unwieldy for me to print") else: print(f"This {num} is a nice number") # In[ ]: def isEven(num): if num%2 == 0: print(f"{num} is even") else: print(f"{num} is odd") isEven(3) isEven(4) # ## Loops # In[ ]: for x in range(10): print(x) # ### in Python 3.X range returns an iterable(Lazy, values on demand, saves memory on longer iteration) # #### in Python 2.7 range returned a list ! (xrange was the iterator version, not as fully featured as the current range) # Full list of differences: http://treyhunner.com/2018/02/python-3-s-range-better-than-python-2-s-xrange/ # In[ ]: for c in "Valdis": print(c) # In[ ]: for k,v in mydict.items(): print(k,v) # In[ ]: printnum(3) # In[ ]: ## Splitting a line of text into words mytext = "A quick brown fox jumped over a sleeping dog" words = mytext.split() # In[ ]: print(words) # In[ ]: ## Print first letter of each word for w in words: print(w[0], w[0].isupper(), w.istitle()) ## istitle() checks every word in a string so not good for unsplit strings # In[ ]: myline="Mr. Sherlock Holmes, who was usually very late in the mornings" # In[ ]: words=myline.split() # In[ ]: words # In[ ]: words[1][0].isupper() # In[ ]: def processLine(line): words = line.split() linegood=False for word in words: if word[0].isupper(): print(word, end='\t') linegood=True if linegood == True: print('') # In[ ]: class MyClass: """A simple example class""" i = 12345 def f(self): #this is important! similar to this in other languages object itself return f'Hello' dir(MyClass) # In[ ]: myc=MyClass() #?myc print(myc.i) print(myc.f()) # In[ ]: class Complex: def __init__(self, realpart, imagpart, name): self.r = realpart self.i = imagpart self.name = name def calcDistance(self, mult): return (self.r**2+self.i**2)**0.5*mult x = Complex(3.0, -4.5, "Complekss") print(x.r, x.i) print(x.calcDistance(5)) print(x.name) # dir(x) dir(Complex) # In[ ]: # TODO List Comprehensions, Dictionary Comperehensions # Generators # File IO # Filter,Map,Apply # Imports, modules # Decorators ! # # Python Resources # ![Learning](img/Learn-Python-Programming-Language.png) # ## Tutorials Begginner to Intermediate # # * https://automatetheboringstuff.com/ - Anything by Al Sweigart is great # * http://newcoder.io/tutorials/ - 5 sets of practical tutorials # * [Think Like a Computer Scientist](http://interactivepython.org/runestone/static/thinkcspy/index.html) full tutorial # * [Non-Programmers Tutorial for Python 3](https://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_3) quite good for wikibooks # * [Real Python](https://realpython.com/) Python Tutorials for all levels # # # * [Learn Python 3 the Hard Way](https://learnpythonthehardway.org/python3/intro.html) controversial author but very exhaustive, some like this approach # ## More Advanced Python Specific Books # # * [Python Cookbook](https://www.amazon.com/Python-Cookbook-Third-David-Beazley/dp/1449340377) Recipes for specific situations # # * [Effective Python](https://effectivepython.com/) best practices # * [Fluent Python](http://shop.oreilly.com/product/0636920032519.do) **highly recommended**, shows Python's advantages # ## General Best Practices Books # #### (not Python specific) # # * [Code Complete 2](https://www.goodreads.com/book/show/4845.Code_Complete) - Fantastic best practices # * [The Mythical Man-Month](https://en.wikipedia.org/wiki/The_Mythical_Man-Month) - No silver bullet even after 40 years. # * [The Pragmatic Programmer](https://www.amazon.com/Pragmatic-Programmer-Journeyman-Master/dp/020161622X) - More practical advice # * [Clean Code](https://www.amazon.com/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882) - more towards agile # ## Blogs / Personalities / forums # # * [Dan Bader](https://dbader.org/) # * [Reddit Python](https://www.reddit.com/r/python) # ## Exercises/Challenges # * http://www.pythonchallenge.com/ - first one is easy but after that... # * [Advent of Code](https://adventofcode.com/) - yearly programming challenges # * https://projecteuler.net/ - gets very mathematical but first problems are great for testing (Prof. Arnicans used to give extra credit for these...) # ## Questions / Suggestions ? # feel free to pull request