Python Programing Language

What is Python?

Python is a programming language. It is a high-level, interpreted, object-oriented, and dynamic programming language. Python is designed to be highly readable. It is also easy to learn.

Keep in mind

1. Python is case sensitive language. print is not Print.
2. Spacing is important. There will be no error if you do not use the correct indentation.
3. Use error messages to help you learn.

Print function

print("Hello World") # Hello World
print(10) # 10
print(8 + 1.5) # 9.5
print(True) # True
print(None) # None

print function is used to print the output.

Arithmetic Operators

• + Addition
• - Subtraction
• * Multiplication
• / Division
• % Mod (the remainder after dividing)
• ** Exponentiation (note that ^ does not do this operation, as you might have seen in other languages)
• // Divides and rounds down to the nearest integer

Example

print(3 + 5) # 8
print(1 + 2 + 3 * 3) # 12
print(3 ** 2) # 9
print(9 % 2) # 1
print(10 // 3) # 3

Variables and Assignment Operators

Variables are used all the time in Python!

Example

x = 10
y = 20

print(x + y) # 30
print(x - y) # -10
print(x * y) # 200

or

x, y = 10, 20

print(x + y) # 30
print(x - y) # -10
print(x * y) # 200

Variable names rules

1. Variable names cannot start with a number.
2. Variable names cannot contain spaces.
3. Variable names cannot contain special characters.
4. Variable names cannot contain the programing language reserved words.
5. Variable name can contain letters, numbers, and underscores.
6. Variable names can be in snake case.
7. Variable names can be descriptive.

Data Types in Python

• int: Integer
• float: Floating point number
• bool: Boolean
• str: String
• list: List
• dict: Dictionary

Example

x = 10 # int
y = 20.5 # float
z = True # bool
a = "Hello" # str
b = [1, 2, 3] # list
c = {"name": "Adonys", "age": 18} # dict

String methods

The string methods are used to manipulate strings.

isLower()

print("Hello".isLower()) # False
print("hello".isLower()) # True

isUpper()

print("Hello".isUpper()) # False
print("HELLO".isUpper()) # True

format()

print("Hello {0}".format("World")) # Hello World
print("Hello {0}".format(10)) # Hello 10
print("Hello {0}".format(10.5)) # Hello 10.5
print("Hello {0}".format(True)) # Hello True
print("Hello {0}".format(None)) # Hello None

split()

print("Hello World".split()) # ['Hello', 'World']
print("Hello World".split("o")) # ['Hell', ' Wrd']

Handling Errors

Try Statement

We can use try statements to handle exceptions. There are four clauses you can use (one more in addition to those shown in the video).

• try: This is the only mandatory clause in a try statement. The code in this block is the first thing that Python runs in a try statement.
• except: If Python runs into an exception while running the try block, it will jump to the except block that handles that exception.
• else: If Python runs into no exceptions while running the try block, it will run the code in this block after running the try block.
• finally: Before Python leaves this try statement, it will run the code in this finally block under any conditions, even if it's ending the program. E.g., if Python ran into an error while running code in the except or else block, this finally block will still be executed before stopping the program.

try:
    # some code
except (ValueError, KeyboardInterrupt):
    # some code

Example

try:
    print(10 / 0)
except ZeroDivisionError:
    print("You cannot divide by zero!")