Key Takeaways

1. A variable  is a named location reserved to store values in the memory. A variable is created or initialized automatically when you assign a value to it for the first time. (2.1.4.1)
2. Each variable must have a unique name - an identifier. A legal identifier name must be a non-empty sequence of characters, must begin with the underscore(_), or a letter, and it cannot be a Python keyword. The first character may be followed by underscores, letters, and digits,. Identifiers in Python are case-sensitive. (2.1.4.1)
3. Python is a dynamically-typed language, which means you don't need to delcare variables in it. (2.1.4.3) To assign values to variables, you can use a simple assignment operator in the form of the equal (=) sign, i.e., var = 1
4. You ca also use compound assignment operators (shortcut operators) to modify values assigned to variables, e.g., var += 1, or var /= 5 * 2. (2.1.4.8.)
5. You can assign new values to already existing variables using the assignment operator or one of the compound operators, e.g.: (2.1.4.5)

   var = 2

   print(var)

   var = 3

   print(var)

   var += 1

   print(var)

6. You can combine text and variables using the + operator, and use the print() function to output strings and variables, e.g.: (2.1.4.4)
    

   var = "007"

   print("Agent " + var)

Exercise 1

What is the output of the following snippet?
 

var = 2

var = 3

print(var)

3

Exercise 2

Which of the following variable names are illegal in Python? 

 

my_var

m

101 - incorrect (starts with a digit)

averylongvariablename

m101

m 101 - incorrect (contains a space)

Del

del - Incorrect (is a keyword)

Exercise 3

What is the output of the following snippet?

a = '1'

b = "1"

print(a + b)

11 it prints them next to each other does not add them. 

Exercise 4

What is the output of the following snippet?

a = 6

b = 3

a /= 2 * b

print(a)

1.0
2 * b = 6
a = 6 → 6 / 6 = 1.0