Python Programming
I have received a ton of requests to make a Python programming tutorial in which I teach pretty much everything in one video.
I’ll cover modules, comments, print, arithmetic operators, order of operation, lists, tuples, dictionaries, conditional operators, logical operators, if, else, elif, loops, for, while, break, continue, functions, return, readline(), string operators, file i/o, classes, objects and much more.
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Cheat Sheet
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# import is used to make specialty functions available # These are called modules import random import sys import os # Hello world is just one line of code # print() outputs data to the screen print("Hello World") ''' This is a multi-line comment ''' # A variable is a place to store values # Its name is like a label for that value name = "Derek" print(name) # A variable name can contain letters, numbers, or _ # but can't start with a number # There are 5 data types Numbers, Strings, List, Tuple, Dictionary # You can store any of them in the same variable name = 15 print(name) # The arithmetic operators +, -, *, /, %, **, // # ** Exponential calculation # // Floor Division print("5 + 2 =", 5+2) print("5 - 2 =", 5-2) print("5 * 2 =", 5*2) print("5 / 2 =", 5/2) print("5 % 2 =", 5%2) print("5 ** 2 =", 5**2) print("5 // 2 =", 5//2) # Order of Operation states * and / is performed before + and - print("1 + 2 - 3 * 2 =", 1 + 2 - 3 * 2) print("(1 + 2 - 3) * 2 =", (1 + 2 - 3) * 2) # A string is a string of characters surrounded by " or ' # If you must use a " or ' between the same quote escape it with \ quote = "\"Always remember your unique," # A multi-line quote multi_line_quote = ''' just like everyone else" ''' print(quote + multi_line_quote) # To embed a string in output use %s print("%s %s %s" % ('I like the quote', quote, multi_line_quote)) # To keep from printing newlines use end="" print("I don't like ",end="") print("newlines") # You can print a string multiple times with * print('\n' * 5) # LISTS ------------- # A list allows you to create a list of values and manipulate them # Each value has an index with the first one starting at 0 grocery_list = ['Juice', 'Tomatoes', 'Potatoes', 'Bananas'] print('The first item is', grocery_list[1]) # You can change the value stored in a list box grocery_list[0] = "Green Juice" print(grocery_list) # You can get a subset of the list with [min:up to but not including max] print(grocery_list[1:3]) # You can put any data type in a a list including a list other_events = ['Wash Car', 'Pick up Kids', 'Cash Check'] to_do_list = [other_events, grocery_list] print(to_do_list) # Get the second item in the second list (Boxes inside of boxes) print(to_do_list[1][1]) # You add values using append grocery_list.append('onions') print(to_do_list) # Insert item at given index grocery_list.insert(1, "Pickle") # Remove item from list grocery_list.remove("Pickle") # Sorts items in list grocery_list.sort() # Reverse sort items in list grocery_list.reverse() # del deletes an item at specified index del grocery_list[4] print(to_do_list) # We can combine lists with a + to_do_list = other_events + grocery_list print(to_do_list) # Get length of list print(len(to_do_list)) # Get the max item in list print(max(to_do_list)) # Get the minimum item in list print(min(to_do_list)) # TUPLES ------------- # Values in a tuple can't change like lists pi_tuple = (3, 1, 4, 1, 5, 9) # Convert tuple into a list new_tuple = list(pi_tuple) # Convert a list into a tuple # new_list = tuple(grocery_list) # tuples also have len(tuple), min(tuple) and max(tuple) # DICTIONARY or MAP ------------- # Made up of values with a unique key for each value # Similar to lists, but you can't join dicts with a + super_villains = {'Fiddler' : 'Isaac Bowin', 'Captain Cold' : 'Leonard Snart', 'Weather Wizard' : 'Mark Mardon', 'Mirror Master' : 'Sam Scudder', 'Pied Piper' : 'Thomas Peterson'} print(super_villains['Captain Cold']) # Delete an entry del super_villains['Fiddler'] print(super_villains) # Replace a value super_villains['Pied Piper'] = 'Hartley Rathaway' # Print the number of items in the dictionary print(len(super_villains)) # Get the value for the passed key print(super_villains.get("Pied Piper")) # Get a list of dictionary keys print(super_villains.keys()) # Get a list of dictionary values print(super_villains.values()) # CONDITIONALS ------------- # The if, else and elif statements are used to perform different # actions based off of conditions # Comparison Operators : ==, !=, >, <, >=, <= # The if statement will execute code if a condition is met # White space is used to group blocks of code in Python # Use the same number of proceeding spaces for blocks of code age = 30 if age > 16 : print('You are old enough to drive') # Use an if statement if you want to execute different code regardless # of whether the condition ws met or not if age > 16 : print('You are old enough to drive') else : print('You are not old enough to drive') # If you want to check for multiple conditions use elif # If the first matches it won't check other conditions that follow if age >= 21 : print('You are old enough to drive a tractor trailer') elif age >= 16: print('You are old enough to drive a car') else : print('You are not old enough to drive') # You can combine conditions with logical operators # Logical Operators : and, or, not if ((age >= 1) and (age <= 18)): print("You get a birthday party") elif (age == 21) or (age >= 65): print("You get a birthday party") elif not(age == 30): print("You don't get a birthday party") else: print("You get a birthday party yeah") # FOR LOOPS ------------- # Allows you to perform an action a set number of times # Range performs the action 10 times 0 - 9 for x in range(0, 10): print(x , ' ', end="") print('\n') # You can use for loops to cycle through a list grocery_list = ['Juice', 'Tomatoes', 'Potatoes', 'Bananas'] for y in grocery_list: print(y) # You can also define a list of numbers to cycle through for x in [2,4,6,8,10]: print(x) # You can double up for loops to cycle through lists num_list =[[1,2,3],[10,20,30],[100,200,300]]; for x in range(0,3): for y in range(0,3): print(num_list[x][y]) # WHILE LOOPS ------------- # While loops are used when you don't know ahead of time how many # times you'll have to loop random_num = random.randrange(0,100) while (random_num != 15): print(random_num) random_num = random.randrange(0,100) # An iterator for a while loop is defined before the loop i = 0; while (i <= 20): if(i%2 == 0): print(i) elif(i == 9): # Forces the loop to end all together break else: # Shorthand for i = i + 1 i += 1 # Skips to the next iteration of the loop continue i += 1 # FUNCTIONS ------------- # Functions allow you to reuse and write readable code # Type def (define), function name and parameters it receives # return is used to return something to the caller of the function def addNumbers(fNum, sNum): sumNum = fNum + sNum return sumNum print(addNumbers(1, 4)) # Can't get the value of rNum because it was created in a function # It is said to be out of scope # print(sumNum) # If you define a variable outside of the function it works every place newNum = 0; def subNumbers(fNum, sNum): newNum = fNum - sNum return newNum print(subNumbers(1, 4)) # USER INPUT ------------- print('What is your name?') # Stores everything typed up until ENTER name = sys.stdin.readline() print('Hello', name) # STRINGS ------------- # A string is a series of characters surrounded by ' or " long_string = "I'll catch you if you fall - The Floor" # Retrieve the first 4 characters print(long_string[0:4]) # Get the last 5 characters print(long_string[-5:]) # Everything up to the last 5 characters print(long_string[:-5]) # Concatenate part of a string to another print(long_string[:4] + " be there") # String formatting print("%c is my %s letter and my number %d number is %.5f" % ('X', 'favorite', 1, .14)) # Capitalizes the first letter print(long_string.capitalize()) # Returns the index of the start of the string # case sensitive print(long_string.find("Floor")) # Returns true if all characters are letters ' isn't a letter print(long_string.isalpha()) # Returns true if all characters are numbers print(long_string.isalnum()) # Returns the string length print(len(long_string)) # Replace the first word with the second (Add a number to replace more) print(long_string.replace("Floor", "Ground")) # Remove white space from front and end print(long_string.strip()) # Split a string into a list based on the delimiter you provide quote_list = long_string.split(" ") print(quote_list) # FILE I/O ------------- # Overwrite or create a file for writing test_file = open("test.txt", "wb") # Get the file mode used print(test_file.mode) # Get the files name print(test_file.name) # Write text to a file with a newline test_file.write(bytes("Write me to the file\n", 'UTF-8')) # Close the file test_file.close() # Opens a file for reading and writing test_file = open("test.txt", "r+") # Read text from the file text_in_file = test_file.read() print(text_in_file) # Delete the file os.remove("test.txt") # CLASSES AND OBJECTS ------------- # The concept of OOP allows us to model real world things using code # Every object has attributes (color, height, weight) which are object variables # Every object has abilities (walk, talk, eat) which are object functions class Animal: # None signifies the lack of a value # You can make a variable private by starting it with __ __name = None __height = None __weight = None __sound = None # The constructor is called to set up or initialize an object # self allows an object to refer to itself inside of the class def __init__(self, name, height, weight, sound): self.__name = name self.__height = height self.__weight = weight self.__sound = sound def set_name(self, name): self.__name = name def set_height(self, height): self.__height = height def set_weight(self, height): self.__height = height def set_sound(self, sound): self.__sound = sound def get_name(self): return self.__name def get_height(self): return str(self.__height) def get_weight(self): return str(self.__weight) def get_sound(self): return self.__sound def get_type(self): print("Animal") def toString(self): return "{} is {} cm tall and {} kilograms and says {}".format(self.__name, self.__height, self.__weight, self.__sound) # How to create a Animal object cat = Animal('Whiskers', 33, 10, 'Meow') print(cat.toString()) # You can't access this value directly because it is private #print(cat.__name) # INHERITANCE ------------- # You can inherit all of the variables and methods from another class class Dog(Animal): __owner = None def __init__(self, name, height, weight, sound, owner): self.__owner = owner self.__animal_type = None # How to call the super class constructor super(Dog, self).__init__(name, height, weight, sound) def set_owner(self, owner): self.__owner = owner def get_owner(self): return self.__owner def get_type(self): print ("Dog") # We can overwrite functions in the super class def toString(self): return "{} is {} cm tall and {} kilograms and says {}. His owner is {}".format(self.get_name(), self.get_height(), self.get_weight(), self.get_sound(), self.__owner) # You don't have to require attributes to be sent # This allows for method overloading def multiple_sounds(self, how_many=None): if how_many is None: print(self.get_sound) else: print(self.get_sound() * how_many) spot = Dog("Spot", 53, 27, "Ruff", "Derek") print(spot.toString()) # Polymorphism allows use to refer to objects as their super class # and the correct functions are called automatically class AnimalTesting: def get_type(self, animal): animal.get_type() test_animals = AnimalTesting() test_animals.get_type(cat) test_animals.get_type(spot) spot.multiple_sounds(4) |
i love the info. well put. just starting to learn python. again tks alot
Thank you 🙂 You are very welcome
Derek,
Where is the source code location for these tutorials? I think I saw a link in one of the videos, but now I can’t seem to locate them.
Thanks,
Michael
Derek,
Nevermind, I eventually found it. I had a bug running video #8, OOP, and found when I clicked “more” on youtube, a note for the source code was listed.
Thanks,
Michael
I’m glad you found it. Sorry I couldn’t help sooner.
Jeepers you are awesome. I hope you will make a video on how to manipulate postgreSQL databases with Python. I might use Django when I get some Python learned. I think pg is more intuitive to code, can’t stand to look at mysql commands. I want to make a database driven website, already know html, css, and some postgres and javascript.
Thank you 🙂 I’ll see what I can do. I’m going to cover NodeJS very soon and explore all that you can do with it.
Thanks a lot derek.