reading-notes

Getting Started with Python

References

Submission

List any features of Python that you like/dislike most so far.
- Python does not require you to use reserved words to declare variables
  - You create a variable whenever you assign something a value
  - I like this because I do not need to worry about forgetting to add a let, const, or var in front of something that I want to use as a variable
- Python does not require you to define data types and allows mixing of data types together
  - I am neutral on this
  - On one hand, this means I can pack a lot of data into something like an array
  - On the other hand, this means that if I am not careful about remembering what types of data I have inside an array I could end up creating errors in my program
- Python allows you to explicitly state if a variable is in the global scope via the global reserved word
  - I like this because I can create global variables to be reused/referenced by my programs within functions without having to worry about returning the value and passing it back to a global variable
- Python allows multiple values to be assigned to the same variable and will reference whichever is the most recent
  - I do like that this makes variables easy to update, but the downside is that you need to remember exactly which variable you are calling
    - For example, if you want to call a variable x and have many x’s throughout the program, you may call the wrong one
- Python requires you to indent correctly in order to create a block of code
  - I don’t like this as much since messing up spacing even a little bit will throw off the code and create errors
List some of the ways that Python is similar and different to JavaScript.
- Variables
  - Both
    - Variables can be within the global scope of the program or local scope of a function
  - Python
    - Can assign multiple variables values in one line
    - Can reuse variable names and have that name hold multiple values
    - Does not require a variable be declared with a reserved word
    - Can declare a global variable within a function
  - JS
    - Cannot assign multiple variables values in a single line of code
    - Requires variables be declared with reserved words
    - Global variables must be declared within the global scope outside of a function
- Functions
  - Both
    - Require functions be declared
  - Python
    - Requires proper in dentation for function to be read properly
    - Uses :
    - Has lambda functions that allow you to create anonymous functions within other functions
  - JS
    - Indentation is for readability only and does not impact the functions execution
    - Uses ;

Notes

Assignment
- Python Syntax to Python Lambda Functions
- Complete Python Exercises
- Complete remaining Python Tutorial

Indentation

Python uses indentation to indicate a block of code
- Therefore, indentation is important to the functionality of Python, not just for readability
Indentation is usually 4 spaces

Variables

There are no commands for declaring a variable in Python
You create a variable whenever you assign a value to something (i.e. x = 5)

Comments

Comments are created with #
Python has no syntax for multiline comments
- A # must proceed each comment line
There is a work around that will allow you to use a string literal not assigned a variable to create a multiline comment
```
"""
This is a comment
written in
more than just one line
"""
print("Hello, World!")
```

Variables

Created by assigning something a value

You can specify the type of data a variable should be via casting

x = str(3)    # x will be '3'
y = int(3)    # y will be 3
z = float(3)  # z will be 3.0

String variables can use double or single quotes
Variable names are case-sensitive

Python will allow you to assign values to multiple variables in one line

x, y, z = "A", "B", "C"
print(x) #prints x
print(y) #prints y
print(z) #prints z

You can assign the same value to multiple variables

x = y = z = "Orange"
print(x)
print(y)
print(z)

You can unpack a collection of values and extract each value into variables

fruits = ["apple", "banana", "cherry"]
x, y, z = fruits
print(x)
print(y)
print(z)

print() is the output variable in Python
Variables created outside a function are in the global scope of the program
Variables created within a function are in the local scope of the function
- NOTE: can use the global keyword to create a global variable inside a function

Data Types

Type	Name
Text	`str`
Numeric	`int, float, complex`
Sequence	`list, tuple, range`
Mapping	`dict`
Set	`set, frozenset`
Boolean	`bool`
Binary	`bytes, bytearray, memoryview`
None	`NoneType`

Numbers

int = whole number
float = decimal number
complex = combo of letters and numbers

Random number generation:

import random
print(random.randrange(1, 10)) #prints random numbers between 1 and 10

Strings

Single or double quotes
Assign multiline strings using triple quotes """<string>"""
Strings are treated as arrays by Python
Loop through string
```
for x in "banana":
  print(x)
```
String Length
```
a = "Hello, World!"
  print(len(a))
```

Check contents of string

# Contains value
txt = "The best things in life are free!"
print("free" in txt)

# Does NOT contain value
txt = "The best things in life are free!"
print("expensive" not in txt)

Sting slicing

b = "Hello, World!"
#From beginning
print(b[:5]) #Hello
#From end
print(b[6:]) #World!
#Between
print(b[2:6]) #ello

Modify strings
- .upper() = to uppercase
- .lower() = to lowercase
- .strip() = remove whitespace
- .replace(val1, val2) = replace val1 with val2
- .split("delimiter") = break the string apart at the delimiter (i.e. ,, ` , :`, etc.)
Concatenate strings
- str1 + str2 = str1str2
- str1 + " " + str2 = str1 str2
Insert numbers into string
- Use {} as place holders combined with .format(variable)
```
age = 36
txt = "My name is John, and I am {}"
print(txt.format(age))
```

Escape Characters for strings

Code	Result
'	Single Quote
\	Backslash
\n	New Line
\r	Carriage Return
\t	Tab
\b	Backspace
\f	Form Feed
\ooo	Octal value
\xhh	Hex value

Python Assignment Operators

Operator	Example	Same As
=	x = 5	x = 5
+=	x += 3	x = x + 3
-=	x -= 3	x = x - 3
*=	x *= 3	x = x * 3
/=	x /= 3	x = x / 3
%=	x %= 3	x = x % 3
//=	x //= 3	x = x // 3
**=	x **= 3	x = x ** 3
&=	x &= 3	x = x & 3
\|= x	\|= 3	x = x \| 3
^=	x ^= 3	x = x ^ 3
»=	x »= 3	x = x » 3
«= x	«= 3	x = x « 3

Lists

4 Types
- List is a collection which is ordered and changeable. Allows duplicate members.
- Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
- Set is a collection which is unordered, unchangeable*, and unindexed. No duplicate members.
- Dictionary is a collection which is ordered** and changeable. No duplicate members.