Lesson — Foundation

METHODS KI
POORI LIST.

40+ string methods — case, search, check, split, join. Interview wale sabse-kaam-ke methods, ek jagah, Hinglish me.

⏱ 25 min• BeginnerPrerequisite: Strings

WHY: interview me methods poochte hain

"Email valid hai?", "Mobile me sirf digits hain?", "Order-ID ka prefix nikalo" — aise real kaam string methods se hote hain. MNC interviews me split-join aur isdigit-check wale questions pakke aate hain.

email = "aman@gmail.com"
print(email.endswith(".com"))  # True
print(email.split("@"))  # ['aman', 'gmail.com']

Case badalna: 6 methods

Naam, sheher, input — sabka case ek jaisa karo taaki compare aur search sahi ho.

Method	Kya karta hai	Example
`capitalize()`	Pehla bada, baaki chhota	`"aman".capitalize()`
`casefold()`	Strict compare ke liye chhota	`"Aman".casefold()`
`lower()`	Sab chhota	`"Lucknow".lower()`
`upper()`	Sab bada	`"up".upper()`
`title()`	Har word bada	`"old delhi".title()`
`swapcase()`	Ulta kar deta hai	`"AbC".swapcase()`

Dhoondhna: find, index, count

Text ke andar position ya ginti chahiye to ye teen. find() na mile to -1 deta hai, index() error dega — farak yaad rakho.

order = "SWIGGY-4821-SWIGGY"
print(order.find("SWIGGY"))  # 0
print(order.rfind("SWIGGY"))  # 12 (right se)
print(order.count("SWIGGY"))  # 2
print(order.startswith("SW"))  # True
print(order.endswith("21"))  # True

Check karna: is-wale methods

Form validation ka khazana — True/False me jawab. Mobile number, PAN, pincode check karne ke kaam ke.

Method	Kya karta hai	Example
`isalpha()`	Sirf letters?	`"abc".isalpha()`
`isdigit()`	Sirf digits?	`"99199".isdigit()`
`isalnum()`	Letters ya digits?	`"abc123".isalnum()`
`islower()`	Sab chhota?	`"abc".islower()`
`isupper()`	Sab bada?	`"ABC".isupper()`
`isspace()`	Sirf space?	`" ".isspace()`
`istitle()`	Title-case?	`"New Delhi".istitle()`

mobile = "9919917791"
print(mobile.isdigit() and len(mobile) == 10)  # True

pan = "ABCDE1234F"
print(pan[:5].isalpha() and pan[5:9].isdigit())  # True

Todna-jodna aur saaf karna

CSV line, date, full name — split() todta hai, join() jodta hai. Extra space aur code ke liye strip/pad wale.

Method	Kya karta hai	Example
`split(x)`	Tukde karke list	`"a,b".split(",")`
`rsplit(x)`	Right se todna	`"a,b,c".rsplit(",", 1)`
`splitlines()`	Lines todna	`"a\nb".splitlines()`
`join(list)`	Jodna	`"-".join(["a", "b"])`
`strip()`	Dono side space kaatna	`" a ".strip()`
`lstrip() / rstrip()`	Ek side kaatna	`" a ".lstrip()`
`replace(a, b)`	Badalna	`"a-b".replace("-", " ")`
`partition(x)`	3 hisse: pehle, match, baad	`"a=b=c".partition("=")`
`zfill(n)`	Zero se bharna	`"42".zfill(5)`

row = " Ramesh, Lucknow, 226001 "
parts = [p.strip() for p in row.split(",")]
print(parts)
print(" | ".join(parts))

Try it: email validatorMethods combine karo

main.pyOptional input

Run Python dabayein

Quick check

String Lucknow ko poora chhota likhne ki expression likho.

lower method — dot ke baad naam, phir parentheses.

🎓

Guido-style insight: Methods yaad nahi, pehchano. 40+ methods ratne ki zaroorat nahi — pattern samjho: case/search/check/split. Kaam pade to docs kholo, sharam kaisi?

email = "  Aman@Gmail.COM  "
email = email.strip().lower()
print(email.split("@"))  # ['aman', 'gmail.com']

MNC tip: Method-chaining (strip().lower().split()) ek line me likh kar dikhao.

Common mistakes

find() aur index() confuse karna — na mile to ek -1 deta hai, doosra error.
isdigit() negative ya decimal par False dega — "-5" digit nahi hai.
Methods original string nahi badalte — result wapas variable me rakho.

Methods yaad ho gaye?

Ab multiple values store karo — lists ki baari.

METHODS KIPOORI LIST.