Code-Memo

Variables in Python

x = 5
y = "Hello, World!"

Variable Naming Rules

Must start with a letter or an underscore
Cannot start with a number
Can only contain alphanumeric characters and underscores
Case-sensitive

my_var = 10
_my_var = 20
MY_VAR = 30
myVar2 = 40

Dynamic Typing

Python is dynamically typed, meaning you don’t need to declare the type of a variable. The type is inferred from the value.

x = 10      # int
x = "text"  # str

Data Types

Python has several built-in data types:

Numeric Types

int: Integer values
```
x = 10
```
float: Floating-point values
```
y = 10.5
```
complex: Complex numbers
```
z = 1 + 2j
```

Sequence Types

str: String
```
name = "Alice"
```
list: Ordered, mutable collection
```
my_list = [1, 2, 3]
```
tuple: Ordered, immutable collection
```
my_tuple = (1, 2, 3)
```

Mapping Type

dict: Key-value pairs
```
my_dict = {"name": "Alice", "age": 25}
```

Set Types

set: Unordered, unique collection
```
my_set = {1, 2, 3}
```
frozenset: Immutable set
```
my_frozenset = frozenset([1, 2, 3])
```

Boolean Type

bool: True or False
```
is_active = True
```

None Type

NoneType: Represents the absence of a value
```
x = None
```

Input

List Comprehensions: To read multiple values into a list.

numbers = list(map(int, input("Enter multiple numbers: ").split()))
print(numbers)

Reading from File: If the input is from a file, use open() and read() methods.

with open('input.txt', 'r') as file:
    data = file.read()
print(data)

Input Validation:

try:
    age = int(input("Enter your age: "))
except ValueError:
    print("Invalid input. Please enter a number.")