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Al Sweigart/01 Python Basics/Notes.MD

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+# Learning with Al Sweigart - Automate the boring stuff with Python
+REPL, explained;
+Read Evaluate Print Loop, this lets us run or execute Python instructions one at time and instantly shows it's output.
+
+Basic Math Operators in Python 
+
+| Operator | Operation | Example |
+|:----|:-----------------:|:---------------:|
+| ** | Exponent(raised to the power) | 2 ** 3 = 8 |
+| %  | Modulus/Remainder | 22 % 8 i.e 2 rem 6 = 6 |            
+| // | Integer division/round up | 22 // 8 = 2.75, 2.75 rounds up to 2|
+| /  | Division | 22 / 8 = 2.75 |                       
+| *  | Multiplication | 3 * 5 = 15 |                         
+| -  | Subtraction | 5 - 2 = 3 |                           
+| +  | Addition | 5 + 5 = 10 |                          
+
+```py
+exponent = 8 ** 4
+modulus = 13 % 2
+round_up = 93 // 5
+divide = 169 / 13
+multiply = 12 * 12
+subtract = 256 - 13
+add = 101 + 102
+# print(round_up)
+```
+
+The order of Operations in python are called **Precedence**, think, **BODMAS** in Python, __i.e__, **PEDMAS**, in that order, the 
+former taking precedence; The __(**)__ is evaluated first, then __(*)__, __(/)__, __(//)__, __(%)__ operators are evaluated next; from left 
+to the right. And the __(+)__, __(-)__ operators are evaluated last _(also from left to right)_.
+
+**Parenthesis ()**, are used to override the order of things, operations in brackets __()__, are treated first, 
+_also from left to the right_.
+
+Whitespace in between values do not matter and are ignored in Python **_(except for indentation -starting on a new line)_**,
+but a single space is convention and is overlooked.
+
+```py
+try1= 2 + 2
+try1 = 9   +   9
+print(try1)
+```
+
+### Integer, **Floating-Points _(Floats)_**, and String Data Types
+A data type is a category for values, and every value belongs to exactly one datatype.
+
+### Common Data Types
+**Integers _(int)_** -2, -1, 0, 1, 2, 3, .... <br>
+**floating-points _(floats)_** -1.25, -1.0, -0.5, ... <br>
+**Strings _(str)_** "a", 'b', "c", 'D' 'Hello!'....
+
+Strings are always surrounded in single or double quotes __('')__, or __("")__; **_i.e_**, 
+`'Hello'`, `"Good morning"`, so Python knows where the strings begin and ends, `(' ', or " ")` are called empty strings.
+
+```py
+greetings = "Hello cruel world"
+regards = 'Wish you the very same'
+empty = " "
+print(empty)
+```
+
+### String Concatenation and Replication
+__(+)__ sign is a mathematical operator that sums two or more values of integer types;
+**However**, **_(+)_** sign is also used for **concatenating** or **joining** strings.
+
+```py
+friend1 = 'Middleman'
+friend2 = "Miles"
+friends = friend1 + friend2  # 'Middleman' + "Miles"
+print(friends)
+```
+The __(*)__ operator, when used on one string value and one integer value, it becomes the string replication operator.
+
+```py
+friend3 = 'Angel' * 5
+print(friend3)
+```
+
+### Storing values in variables
+
+A **variable** is like a _box_, this lets us store a single value.
+**Assignments** __(=)__; assigns a value of any known datatype to a variable.
+
+```py
+light_yrs = 40
+print(light_yrs)
+
+nummer = 2
+print(nummer)
+print(light_yrs + nummer + light_yrs)
+
+nummer = nummer + 10
+print(nummer)
+```
+
+A variable is created when a value is stored or assigned to it.
+After that, the variable name can be called as their expressions or by name with other variables and values. When a variable is assigned a new value, the old value is forgotten.
+
+```py
+nummer = 2
+print(nummer)
+nummer = nummer + 10
+print(nummer)
+```
+
+### Variable Names
+
+An ideal Variable name describes the data it contains. One can name a variable
+almost anything, under certain rules ofcourse; Python have some restrictions when it
+comes to name variables. A good Variable in Python follows these rules;
+
+__one word no spaces__ (eg; variable name | variableName) <br>
+use only letters, numbers and the underscore(_) character no hyphens(-). <br>
+variables names can't begin with a number (eg; 15boxes | box15)
+
+Variable names are _case-sensitive_, in the sense that _box_, **BOX**, `Box`, _`bOX`_, are
+different variables. It is a Python convention to start variables with lowercase
+letters. __(eg; Find = 'works ✅' but find = "is preferred")__.
+
+**camelCasing** or **under_score** as variable naming styles are advised.
+
+
+**When there are no more lines of code to execute, the Python program terminates, and stops running.
+When a Python file is ran, it starts from the top, working it's way down, executes the inputted commands
+until the last line, then the Python program exits.**
+
+### Comments
+```py
+# This entire area is commented and won't be executed when ran.
+```
+Python ignores comments, and can be used to leave notes or to explain what a particular line of code does to others.
+
+```py
+# (#) for single line comments
+
+"""
+for multiple lines
+for multiple lines
+for multiple lines
+"""
+
+```
+
+### Print() Function
+The `print()` function displays the string value inside it's parenthesis on the screen when you run the code.
+
+```py
+print('Hello, treacherous world!')
+print('How many fingers am I holding up?')  # Then run
+```
+
+### Input() Function
+The `input()` function waits for the user to type some text on the keyboard and press
+**ENTER**. Here the function asks for a particular datatype, Strings **_(str)_** most times; and
+you can fill it in directly in the terminal.
+
+```py
+myOtherName = input("What is your name? ")  # Stores value to the variable 'myOtherName
+print('Your name is ' + myOtherName)
+'''
+NOTE!!! input() functions are only available in versions of Python3, may not work if running Python2
+'''
+```
+
+### Len() Function
+The `len()` function, you can pass in a string value **(or a variable containing string)**,
+and the function evaluates to the integer value of the total number of characters
+**(letters)** in that string.
+
+```py
+frankOceanSaid = 'I can never make him love me'
+print(len(frankOceanSaid))
+'''
+print() : shows us the output, len(), counts and gives the number of characters
+'''
+```
+
+### Integer + String concatenation errors
+
+```py
+# print('I am ' + 29 + 'years old') # 29 is an integer(int), can only concatenate strings(str).
+```
+
+Python gives an **~~error~~** cuz' the __(+)__ operator can only be used to add two integers
+together or concatenate two strings. You can't add an integer to a string, doesn't
+follow Pythons grammar rules. One can alter the code to print **_integers(int)_** as
+**_stings(str)_**.
+
+### The `str()`, `int()`, and `float()` Functions
+___str()___ : this converts to the string version of the integer within <br>
+__int()__ : also useful for rounding down a floating-point(floats) number
+
+```py
+num = 33
+print('I am ' + str(num) + 'years old')
+
+str(-3.14)  # Python sees a string, equivalent to 'A', and can't be calculated
+str(0)
+int('42')
+int('-99')
+int(7.7) # clearly a float datatype, outputs 7.7 ".7 is > .5", rounds down to 8.
+float('3.14')
+float(10) # turns to 10.0
+```
+
+### Text and number equivalence
+An integer can be equal to a floating point number
+
+44 == '44' :False, '44', is a string <br>
+44 == 44.0 :True, integers(int) rounds down to 44 <br>
+44.0 == 0044.000 :True, ignores the zero's before 44, they are insignificant
+
+Integers and floats are mathematically numbers.
+
+
+## FIRST PROGRAM
+#### This program says hello and asks for users name.
+```py
+print('Hello, cruel world!')
+print('What is your name?')
+
+myName = input()
+print('It is good to meet you, ' + myName)
+
+print('The length of my name has got to be: ')
+print(len(myName))
+
+print('How old are you?')
+myAge = input()
+print('I will be ' + str(int(myAge) + 1) + ' in a year!')
+```

Al Sweigart/01 Python Basics/python problems/test1.py

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+# Write a program that asks the user for their birth year, and prints how old they’ll be in the year 2050.
+
+ask4BirthYear = int(input("What year were you born? "))
+yearConstant = 2050
+print("You are going to be " + str(yearConstant - ask4BirthYear) + " years old in the year 2050")

Al Sweigart/01 Python Basics/python problems/test2.py

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+# Modify test1: also ask for their birth month & day, and tell them whether they've had their birthday
+# yet this year (relative to today). (Work with date arithmetic manually or use datetime.)
+

Al Sweigart/01 Python Basics/python problems/test3.py

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+# Create a “tip calculator”: ask user for bill amount and tip percentage (like “15%”), compute tip and total.
+
+
+
+