Basic Syntax and Variables in Python

Python Python for Data Science Rizwan khan

Variables

Variables in programming are used to store and manage data. They act as containers for values, which can be numbers, text, or more complex data types. You give a variable a name and assign it a value, allowing you to use and manipulate that value throughout your code. For example, x = 5 assigns the value 5 to the variable x. Variables make it easy to reference and work with data efficiently.

Variable Naming Rules:

• Variable names must start with a letter or an underscore (_).
• They cannot start with a number.
• They can only contain alphanumeric characters and underscores (A-Z, a-z, 0-9, and _).
• Variable names are case-sensitive (e.g., myVariable and myvariable are different).

what is meant by Syntax

Syntax in programming refers to the set of rules that define the structure and arrangement of statements in a programming language. It specifies how the symbols, keywords, and characters of a language must be combined to create valid programs. In other words, syntax dictates the correct way to write code so that the compiler or interpreter can understand and execute it. Proper syntax ensures that the code is readable and error-free, following the conventions and standards of the language.

Comments

Comments are used to explain code and are ignored by the Python interpreter. Single-line comments start with "#"

Basic Syntax

Python syntax refers to the set of rules that define how a Python program is written and interpreted. Here are some fundamental elements:

Some examples

print("Hello, World!")

Multi-line comments can be created using triple quotes ''' or """

"""

This is a multi-line comment

that spans several lines.

"""

Variables are used to store data. In Python, you don't need to declare a variable before using it. You just assign a value to a variable.

x = 5

y = "Hello"

print(x)

print(y)

Assigning Values to Variables:

a = 10

b = 3.14

c = "Python"

You can also assign multiple variables in one line:

x, y, z = 1, 2, 3

Updating Variables:

Variables can be updated by reassigning a new value to them

a = 5

a = a + 2 # a is now 7

Variable Types:

Python supports several data types, including:

• Numeric Types: int, float, complex
• Sequence Types: list, tuple, range
• Text Type: str
• Boolean Type: bool

You can check the type of a variable using the type() function.

x = 42

print(type(x)) # Output: <class 'int'>

y = 3.14

print(type(y)) # Output: <class 'float'>

z = "Hello"

print(type(z)) # Output: <class 'str'>

Variable Scope: The scope of a variable is the region of the code where it is recognized. Variables defined inside a function are local, while those defined outside are global.

# Global variable

name = "Alice"

def greet():

# Local variable

age = 25

print("Name:", name)

print("Age:", age)

greet()

print(name) # This will work

# print(age) # This will cause an error because 'age' is local to the function 'greet'

Conclusion

Understanding the basic syntax and how to work with variables is the foundation of learning Python. With this knowledge, you can start writing simple Python programs and gradually move on to more complex tasks. Keep practicing and exploring more Python features to enhance your programming skills.

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