# MLE_VISOR2 Week 1 Note

## CONSTANTS, VARIABLES, DATA TYPES

## 1. CONSTANTS and VARIABLES:
##### A constant is a type of variables that its value can't be change while with variables we can change what data its store in the memory

##### Ex:

2021 is a constant:

print(2021)

year is a variable:

year = 'This is the current year'
print(year)

year = 2021
print(year)

## 2. DATA TYPES:
You can check your data types using type()

type(4) 
type(4.41)
type('Lalalala')
type(True)

### 1. NUMBERS:
##### Numerical data types can belong to 2 different numerical types: int and float

type(4) #return int
type(4.41) #return float

We can also conver between these 2 data types

int(4.41) #return 4
float(4) #return 4.0

Mathematics operation for numbers: we can assign a number to a variable and calculate with it

score = 4
score + 1    #plus
score - 2    #minus
score * 2    #multiplication
score/2      #divine
score % 2    #find the remainder
score//2     #interger division  

### 2. Strings:
##### String is a sequence of characters surround by quotes
You can use single quotes, double quotes (in case the string containt single quotes) and triple quotes (to have multiple lines in string)

print('CoderSchool')
print("I'm tired!!!")
print('''I'm 
still 
tired
but you need to read it multiple lines
to get tired too :D''')

##### Indexing allows you to access invidual characters by using a numeric value.

###### The formula is W[start:stop:step]

- 'start' is the index of the first character you want to find (default by 0, in Python we start counting at 0)
- 'stop' is the index of the last character you want to find (defaul by the length of the string)
- step is the increment you want in the index (default by 1).

x = 'CoderSchool'
x[1:4:2]
x[:5]
x[:]

##### String is also immutable, which means you can't do this

#change the fourth character of x to C and get 'CodCrSchool'
x = 'CoderSchool'
x[3] = 'C'
#to do this you will need to change the whole string
x = 'CodCrSchool'
x[3]
#pretty tired :(

### 3. Boolean:
##### Boolean is the result when you compare two variable/constants and it will return True/False. However you can't compare two variables with different data types

a = 5
b = 6
a < b     #return True
a > b     #return False

##### True will be equal to 1 and False will be equal to 0