Variables & Dynamic Typing
Python mein variable declare karne ke liye koi type likhna zaroori nahi — x = 5 likhte hi Python khud samajh leta hai x ek integer hai. Yehi variable baad mein x = "hello" likhne se string ban sakta hai — "dynamic typing" isi ko kehte hain.
Python ke basic types: int (whole numbers), float (decimals), str (text), bool (True/False), aur None (Python ka "null" — koi value nahi). type() function se kisi bhi variable ka current type check kar sakte ho.
x = 5 # int
print(type(x)) # <class 'int'>
x = "Hello" # ab x string ban gaya — same variable!
print(type(x)) # <class 'str'>
is_student = True # bool
nothing = None # Python ka "null"
age: int = 25 # type hint (optional) — documentation ke liye, enforce nahi hota- Koi type declaration zaroori nahi — dynamic typing
- Ek variable apni lifetime mein type badal sakta hai
- type() function se current type check karo
Python ek line mein multiple variables assign karne deta hai — bahut concise aur readable, especially swapping values ke liye (bina temp variable ke, jo C mein zaroori hota tha).
a, b, c = 1, 2, 3
print(a, b, c) # 1 2 3
x, y = 5, 10
x, y = y, x # swap! koi temp variable nahi chahiye
print(x, y) # 10 5Python convention hai variables/functions ke liye snake_case (jaise student_name), na ki camelCase (jaise Java/JavaScript mein studentName). Classes ke liye PascalCase use hota hai (jaise StudentRecord).
student_name = "Aarav" # snake_case — Python convention
total_marks = 450
class StudentRecord: # PascalCase — classes ke liye
pass