Lesson 05 � Foundation

BOOLEANS:
TRUE YA FALSE.

Booleans True ya False hote hain � ye decisions ke foundation hain. Har condition, har if/else, har loop boolean expression par depend karta hai. Bina booleans ke code mein decisions lene ka koi tarika nahi hai.

WHY: booleans kyun zaroori hain?

Socho aap ek login system bana rahe ho � username sahi hai ya nahi✓ Password match kar raha hai ya nahi✓ Ye sab boolean questions hain jinka sirf do jawab ho sakte hain: True ya False. Booleans har jagah hain � conditions, loops, arguments, aur function return values sab mein.

WHEN: har decision mein booleans

Har baar jab aap koi condition check karte ho � user ka access level, payment status, form validation � tab boolean use hota hai. Loop chalana ho ya function se value return karni ho, boolean sabse fundamental building block hai.

HOW: booleans in action

Boolean values

is_student = True
has_job = False

print(is_student) # True
print(has_job) # False
print(type(True)) # <class 'bool'>

True aur False Python ke built-in constants hain � capital T aur F se likhte hain. Ye koi string nahi hain, ye actual boolean values hain.

Comparison operators

x = 10

print(x > 5) # True
print(x == 10) # True
print(x != 5) # True
print(x < 3) # False
print(x >= 10) # True
print(5 <= 3) # False

Comparison operators hamesha True ya False return karte hain. == equality check hai, != inequality check hai. >= aur <= mein equal sign ke saath comparison hota hai.

Logical operators

age = 25
has_id = True

# and � dono True hone chahiye
print(age >= 18 and has_id) # True

# or � kam se ek True ho
print(age < 18 or has_id) # True

# not � ulta kar deta hai
print(not has_id) # False
print(not False) # True

and tab True hai jab dono conditions True hon. or tab True hai jab kam se ek condition True ho. not True ko False aur False ko True bana deta hai.

Truthiness � sab kuch boolean ho sakta hai

# Strings
print(bool("hello")) # True
print(bool("")) # False (khali string)

# Numbers
print(bool(42)) # True
print(bool(0)) # False (zero)

# Lists
print(bool([1, 2])) # True
print(bool([])) # False (khali list)

# None
print(bool(None)) # False

Python mein har value ek "truthy" ya "falsy" hoti hai. Khali strings, zero, None, aur khali collections False hoti hain. Baaki sab True. Ye concept conditions mein bahut kaam aata hai � jaise if my_list: se check kar sakte ho ki list mein kuch hai ya nahi.

Common mistakes

• true ya True galat hai � sirf True (capital T) sahi hai. Same for False.
• == aur = mein confusion � == comparison hai, = assignment hai.
• and/or/not lowercase mein hote hain; AND/OR/NOT invalid hai.
• Boolean ko string se compare mat karo � "True" == True False hoga, kyunki ek string hai aur doosra boolean.