Shartlar: if, elif, else

6-bob 39 kod bloki 2918 so'z

Taqqoslash: savolga True yoki False

Dastur qaror qabul qilishi uchun avval savol berish kerak: "ball 60 dan katta yoki tengmi?". Bunday savolning javobi — True (rost) yoki False (yolg'on).

ball = 72
print(ball >= 60)
print(ball == 100)
print(ball != 100)

True
False
True

ball = 72
if ball = 100:
    print("A'lo")

SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<kitob>, line 2)

Python matematikadagi kabi zanjir taqqoslashni tushunadi:

yosh = 17
print(14 <= yosh < 18)

True

Satrlar ham solishtiriladi. Katta va kichik harf farq qiladi:

print("ali" == "ali")
print("Ali" == "ali")
print("Ali".lower() == "ali")

True
False
True

and, or, not

Bir nechta shartni birlashtirish uchun:

yosh = 20
pasport = True
print(yosh >= 18 and pasport)

kun = "yakshanba"
print(kun == "shanba" or kun == "yakshanba")

tolangan = False
print(not tolangan)

True
True
True

kun = "dushanba"
if kun == "shanba" or "yakshanba":
    print("Dam olish kuni!")

Dam olish kuni!

kun = "dushanba"
if kun == "shanba" or kun == "yakshanba":
    print("Dam olish kuni!")
else:
    print("Ish kuni")

Ish kuni

if: agar ... bo'lsa

ball = int(input("Ball: "))
if ball >= 60:
    print("Imtihondan o'tdingiz!")
print("Dastur tugadi")

Ball: 72
Imtihondan o'tdingiz!
Dastur tugadi

Tuzilishi:

1. if, keyin shart, oxirida ikki nuqta :.
2. Shart rost bo'lganda bajariladigan qatorlar 4 ta probel ichkarida (chekinish, indentation) yoziladi.
3. Chekinishsiz qator — if ga tegishli emas, u har doim bajariladi.

ball = int(input("Ball: "))
if ball >= 60:
    print("Imtihondan o'tdingiz!")
print("Dastur tugadi")

Ball: 45
Dastur tugadi

45 kiritilganda shart yolg'on: ichkaridagi qator o'tkazib yuborildi, tashqaridagisi bajarildi.

ball = 72
if ball >= 60:
print("O'tdingiz")

IndentationError: expected an indented block after 'if' statement on line 2 (<kitob>, line 3)

ball = 72
if ball >= 60
    print("O'tdingiz")

SyntaxError: expected ':' (<kitob>, line 2)

else: aks holda

ball = int(input("Ball: "))
if ball >= 60:
    print("O'tdingiz")
else:
    print("Afsus, qayta topshirasiz")

Ball: 45
Afsus, qayta topshirasiz

if-else da ikki yo'ldan aynan bittasi bajariladi.

n = int(input("Son: "))
if n % 2 == 0:
    print(n, "juft")
else:
    print(n, "toq")

Son: 17
17 toq

elif: bir nechta yo'l

Ikkidan ortiq holat bo'lsa, elif ("else if") ishlatiladi. Python shartlarni yuqoridan pastga tekshiradi va birinchi rost shartni bajaradi, qolganlarini o'tkazib yuboradi.

ball = int(input("Ball (0-100): "))
if ball >= 86:
    baho = 5
elif ball >= 71:
    baho = 4
elif ball >= 56:
    baho = 3
else:
    baho = 2
print("Baho:", baho)

Ball (0-100): 84
Baho: 4

84 uchun birinchi shart (>= 86) yolg'on, ikkinchisi (>= 71) rost — baho 4. Uchinchi shart ham rost (84 ≥ 56), lekin u tekshirilmaydi, chunki javob topildi.

ball = int(input("Ball: "))
if ball >= 56:
    baho = 3
elif ball >= 71:
    baho = 4
elif ball >= 86:
    baho = 5
print("Baho:", baho)

Ball: 95
Baho: 3

Ichma-ich shartlar

if ichida yana if bo'lishi mumkin. Har bir daraja yana 4 probel ichkariga suriladi:

yosh = int(input("Yosh: "))
guvohnoma = input("Haydovchilik guvohnomasi bormi (ha/yo'q): ")
if yosh >= 18:
    if guvohnoma == "ha":
        print("Mashina ijaraga olishingiz mumkin")
    else:
        print("Avval guvohnoma oling")
else:
    print("18 yoshdan keyin keling")

Yosh: 20
Haydovchilik guvohnomasi bormi (ha/yo'q): ha
Mashina ijaraga olishingiz mumkin

Ko'pincha ichma-ich if ni and bilan soddalashtirish mumkin. Ikki darajadan chuqur ichma-ichlikdan qoching — o'qish qiyinlashadi.

Bo'sh qiymat — yolg'on

2-bobdagi qoidani eslang: bo'sh satr va 0 — False. Bu tekshiruvni qisqartiradi:

ism = input("Ism: ").strip()
if ism:
    print(f"Salom, {ism}!")
else:
    print("Ism kiritilmadi")

Ism: 
Ism kiritilmadi

if ism: — "ism bo'sh bo'lmasa". Bu if ism != "": bilan bir xil, lekin qisqaroq.

Kiritilgan ma'lumotni tekshirish

2-bobda int("abc") dastur yiqilishini ko'rdik. Endi oldindan tekshira olamiz:

matn = input("Yoshingiz: ")
if matn.isdigit():
    yosh = int(matn)
    print("Keyingi yil", yosh + 1, "yoshda bo'lasiz")
else:
    print("Iltimos, faqat raqam kiriting")

Yoshingiz: yigirma
Iltimos, faqat raqam kiriting

a = float(input("a = "))
b = float(input("b = "))
if b == 0:
    print("Nolga bo'lib bo'lmaydi")
else:
    print("a / b =", a / b)

a = 8
b = 0
Nolga bo'lib bo'lmaydi

Qisqa if: bitta qatorda

Ikki qiymatdan birini tanlash uchun qisqa shakl bor:

yosh = 16
holat = "kattalar" if yosh >= 18 else "bolalar"
print(holat)

bolalar

Uni "holat — agar yosh ≥ 18 bo'lsa kattalar, aks holda bolalar" deb o'qing. Faqat oddiy tanlov uchun ishlating.

Loyiha: kvadrat tenglama (to'liq)

4-bobda D < 0 bo'lganda dastur yiqilgan edi. Endi uchta holatni ham ko'rib chiqamiz:

import math

a = float(input("a = "))
b = float(input("b = "))
c = float(input("c = "))

if a == 0:
    print("Bu kvadrat tenglama emas (a = 0)")
else:
    d = b ** 2 - 4 * a * c
    if d > 0:
        x1 = (-b + math.sqrt(d)) / (2 * a)
        x2 = (-b - math.sqrt(d)) / (2 * a)
        print(f"Ikkita ildiz: x1 = {x1}, x2 = {x2}")
    elif d == 0:
        print(f"Bitta ildiz: x = {-b / (2 * a)}")
    else:
        print(f"Haqiqiy ildiz yo'q (D = {d})")

a = 1
b = 2
c = 5
Haqiqiy ildiz yo'q (D = -16.0)

import math

a = float(input("a = "))
b = float(input("b = "))
c = float(input("c = "))

if a == 0:
    print("Bu kvadrat tenglama emas (a = 0)")
else:
    d = b ** 2 - 4 * a * c
    if d > 0:
        x1 = (-b + math.sqrt(d)) / (2 * a)
        x2 = (-b - math.sqrt(d)) / (2 * a)
        print(f"Ikkita ildiz: x1 = {x1}, x2 = {x2}")
    elif d == 0:
        print(f"Bitta ildiz: x = {-b / (2 * a)}")
    else:
        print(f"Haqiqiy ildiz yo'q (D = {d})")

a = 1
b = -6
c = 9
Bitta ildiz: x = 3.0

Endi dastur yiqilmaydi: har qanday kiritishga tushunarli javob beradi.

Xulosa

• Taqqoslash True/False beradi; = bog'laydi, == solishtiradi.
• and — ikkalasi, or — kamida bittasi, not — teskarisi. x == 1 or x == 2 deb to'liq yozing.
• if shart: dan keyin 4 probel chekinish; : ni unutmang.
• elif zanjirida birinchi rost shart yutadi — chegaralarni to'g'ri tartibda yozing.
• if matn: — bo'sh emasligini, matn.isdigit() — raqamligini tekshiradi.

Mashqlar

True/False so'raladigan mashqlarda shartning o'zini chiqaring: print(a > 0).

a = int(input())
print(a > 0)

a = int(input())
print(a % 2 == 1)

a = int(input())
b = int(input())
print(a > 2 and b <= 3)

a = int(input())
b = int(input())
c = int(input())
print(a < b < c)

a = int(input())
b = int(input())
print(a % 2 == 1 and b % 2 == 1)

a = int(input())
print(10 <= a <= 99 and a % 2 == 0)

n = int(input())
a = n // 100
b = n // 10 % 10
c = n % 10
print(a != b and b != c and a != c)

n = int(input())
if n > 0:
    n += 1
print(n)

n = int(input())
if n > 0:
    n += 1
else:
    n -= 2
print(n)

n = int(input())
if n > 0:
    n += 1
elif n < 0:
    n -= 2
else:
    n = 10
print(n)

a = float(input())
b = float(input())
if a > b:
    print(a)
else:
    print(b)

a = float(input())
b = float(input())
if a > b:
    print(a, b)
else:
    print(b, a)

a = float(input())
b = float(input())
c = float(input())
eng = a
if b < eng:
    eng = b
if c < eng:
    eng = c
print(eng)

a = float(input())
b = float(input())
c = float(input())
eng_kichik = a
if b < eng_kichik:
    eng_kichik = b
if c < eng_kichik:
    eng_kichik = c
print(a + b + c - eng_kichik)

ball = int(input())
if ball < 0 or ball > 100:
    print("Xato ball")
elif ball >= 86:
    print(5)
elif ball >= 71:
    print(4)
elif ball >= 56:
    print(3)
else:
    print(2)

y = int(input())
if (y % 4 == 0 and y % 100 != 0) or y % 400 == 0:
    print("Kabisa")
else:
    print("Oddiy")

import math
a = float(input())
b = float(input())
c = float(input())
d = b * b - 4 * a * c
if d > 0:
    x1 = (-b - math.sqrt(d)) / (2 * a)
    x2 = (-b + math.sqrt(d)) / (2 * a)
    print(min(x1, x2), max(x1, x2))
elif d == 0:
    print(-b / (2 * a))
else:
    print("Ildiz yo'q")