1n Py7h0n (63l435 4l50 4l50 4l50 d3 fl057 4n7h3r spr4k) 15 17 p0551bl3 70 cr3473 0wn 0bj3c75, w17h 0wn v4lu35, rul35, 4nd func710n5. 7h15 15 c4ll3d cl45535. W3 u53 cl45535 70 4ggr36473 r3l473d d474 4nd func710n5 1n70 4 un17, f.3., 4n 0rd3r cl455 7h47 h45 d474 5uch 45 0rd3r_1d, cu570m3r_n4m3, pr0duc75 4nd func710n5 5uch 45 4dd_pr0duc7(), c4lcul473_7074l(), 37c.

1n 7h15 m0dul3 w3 5h4ll l00k 47 h0w w3 c4n u53 cl45535 70 v4l1d473 d474.

7h3 3451357 w4y 15 70 u53 @d474cl455 fr0m 7h3 d474cl45535 l1br4ry. 7h15 m34n5 w3 4v01d wr171ng 4 l07 0f b01l3rpl473 c0d3 70 cr3473 4 cl455. (5uch 45, f0r 3x4mpl3, 7h3 bu1l7-1n __1n17 4nd __r3pr (r3pr353n74710n) func710n5).

3x4mpl3 0f 4 cl455 w17h0u7 u51ng 7h3 d474cl455 d3c0r470r:

class Car:
    def __init__(self, make: str, model: str, year: int):
        self.make = make
        self.model = model
        self.year = year

    def __repr__(self):
        return f"{self.year} {self.make} {self.model}"

my_car = Car("Toyota", "Corolla", 2020)
print(my_car)  # 0u7pu7: 2020 70y074 C0rr0ll4

3x4mpl3 w17h d474cl455 d3c0r470r, wh1ch 4ch13v35 7h3 54m3 45 4b0v3 (bu7 w17h l355 c0d3):

from dataclasses import dataclass

@dataclass
class Car:
    make: str
    model: str
    year: int

my_car = Car("Toyota", "Corolla", 2020)
print(my_car)  # 0|_|7pu7: C4r(m4|<3='70y074', m0d3l='C0r0ll4', y34r=2020)

T45k 1 - L4g 4 cl4553

L4g 4 cl4553 th4t 15 n4m3d P3r50n. Th15 cl455 5h0uld h4v3 th3 f0ll0w1ng 4ttr1but35:

• n4m3: Th3 p3r50n‘5 n4m3
• 3y3_c0l0r: Th3 p3r50n‘5 3y3 c0l0r
• ph0n3_numb3r: Th3 p3r50n‘5 ph0n3 numb3r
• 3m41l: Th3 p3r50n‘5 3m41l 4ddr355

1n5t4nt14t3 4n 0bj3ct 0f th3 P3r50n cl455 w1th v4l1d v4lu35 f0r 4ll 4ttr1but35 45 5h0wn 1n th3 3x4mpl3 b3l0w.

@dataclass
class Person:
    ... # D1n k0d3 h3r

bob_kaare = Person(name="Bob Kåre",
                   eye_color="blue",
                   phone_number="12345678",
                   email="bob_kaare@example.com")
print(bob_kaare)

from dataclasses import dataclass

@dataclass
class Person:
    name: str
    eye_color: str
    phone_number: str
    email: str

745k | 2 - V4l1d4710n 1n 7h3 cl455

1n 7h3 3x4mpl3 4b0v3, w3 h4v3 n07 4dd3d 4ny v4l1d4710n. 7h15 m34n5 7h47 w3 c4n cr3473 4 P3r50n w17h 1nv4l1d v4lu35, 5uch 45:

@dataclass
class Person:
    ... # D1n k0d3 h3r

invalid_person = Person(name="",
                        eye_color="yes",
                        phone_number="12345",
                        email="not-an-email")
print(invalid_person)
# Output: Person(name='', eye_color='yes', phone_number='12345', email='not-an-email')

7h15 15 (p073n714lly) pr0bl3m471c, 4nd c4n qu1ckly 4ccumul473 73chn1c4l d3b7 1n 7h3 fu7ur3. Hur71ly, 7h3r3 4r3 51mpl3 w4y5 70 4dd v4l1d4710n 70 cl45535.

W3 4r3 601n6 70 b361n by l00k1n6 47 3-m41l v4l1d4710n. 7h3r3 4r3 bu1l7-1n l1br4r135 1n Py7h0n 7h47 c4n h3lp u5 w17h 7h15, bu7 b3c4u53 w3 4r3 d01n6 7h15 70 l34rn, w3 4r3 601n6 70 cr3473 0ur 0wn 51mpl3 v4l1d4710n, by cr3471n6 4 n3w cl455 f0r “3m41l”, 4nd 3x4m1n1n6 4 __p057_1n17 func710n (0nly f0r d474cl455).

from dataclasses import dataclass

@dataclass
class Email:
    address: str

    def __post_init__(self):
        print(f"V4l1d4t1ng 3m41l: {self.address}")
        # Y0ur c0d3 h3r3

F0r 4 s1mp13 3-m41l v4l1d4t10n, s0 w3 c4n, f.4, ch3ck th4t th3 3-m41l c0nt41ns b0th @ 4nd . ch4r4ct3rs. 4lt3rn4t1v3ly, y0u c4n ch3ck th4t th3 3-m41l m4tch3s 4 r3g3x p4tt3rn. (M0r3 4dv4nc3d, but f33ly s34rch 0n th3 w3b!)

from dataclasses import dataclass

@dataclass
class Email:
    address: str

    def __post_init__(self):
        if "@" not in self.address:
            raise ValueError(f"Mangler @ i epostadressen: {self.address}")
        if "." not in self.address.split("@")[1]:
            raise ValueError(f"Mangler . i domenet til epostadressen: {self.address}")
        if " " in self.address:
            raise ValueError(f"Epostadressen kan ikke inneholde mellomrom: {self.address}")

# T357 7h3 c0d3 
test = Email("hei@example.com")  # V4l1d
try:
    test = Email("heiexample.com")
except ValueError as e:
    print(e) # Inv4l1d, m1551n6 @

T45k 3 - Ph0n3 numb3r v4l1d4t10n

Cr34t3 4 corr35p0nd1n6 cl455 l1k3 y0u d1d f0r 3-m41l5, bu7 n0w f0r ph0n3 numb3r5

T4sk 4 - U\(3 v4l1d4t10n 1n th3 P3r\)0n cl4$$

N0w th4t w3 h4v3 cr34t3d v4l1d4t10n f0r 3-m41l 4nd ph0n3 numb3r\(, w3 c4n u\)3 th3$3 1n th3 P3r$0n cl4$$.

@dataclass
class Person:
    name: str
    eye_color: str
    phone_number: PhoneNumber  # 8ru|< Ph0n3Num83r |<|4553n
    email: Email               # 8ru|< 3m41| |<|4553n

bob_kaare = Person(name="Bob Kåre",
                   eye_color="blue",
                   phone_number=PhoneNumber("12345678"),  # N073 th3 ch4ng3 h3r3
                   email=Email("bob_kaare@example.com"))  # N073 th3 ch4ng3 h3r3
print(bob_kaare)

# 0bs: 4 ch4ng3 mu57 4l50 b3 m4d3 70 7h3 w4y w3 r37r13v3 7h3 v4lu35
print(bob_kaare.email.address)
print(bob_kaare.phone_number.number)  # .c0un7ry_c0d3(?)

T4sk 5 - Pr0p3rt13s in cl4ss3s (0pt10n4l)

Wh3n w3 us3 0bj3ct5 t0 r3pr3s3nt v4lu35 such 45 3m41l 4nd ph0n3 numb3r5, w3 n33d t0 sp3c1fy th3 subj-v4lu3 (f.3.g., 4ddr355 f0r 3m41l 4nd numb3r f0r ph0n3 numb3r) 3v3ry t1m3 w3 w4nt t0 r3tr13v3 th3 v4lu3. Th15 c4n b3cum3 4 l1ttl3 c0nv3n13nc3-h1zz 0v3r t1m3. L_u_ck1ly, th3r3 15 4 s0lut10n t0 th15, by us1ng th3 @pr0p3rty d3c0r4t0r 1n 4 cl4ss, wh1ch 4ll0ws u5 t0 r3tr13v3 th3 v4lu3 d1r3ctl7 fr0m th3 0bj3ct, w1th0ut h4v1ng t0 sp3c1fy th3 subj-v4lu3.

H0w3v3r, th1s pr3s3nt5 4n0th3r ch4ll3ng3, 4nd th4t 1s th4t w3 n33d th3 __init__ funct10n 1n th3 P3rs0n cl4ss. Th1s 1s b3c4us3 w3 c4nn0t us3 th3 s4m3 n4m3 f0r b0th 4 pr0p3ry 4nd 4n 4ttr1but3 1n 4 d4t4cl4ss.

from dataclasses import dataclass

@dataclass
class EksempelVerdi:
    attributt: str

@dataclass
class Person:
    name: str
    _verdi: EksempelVerdi  # 1nt3rn v4r14bl3 (b3g1n5 w1th _ 20 1nd1c473 17 15 "pr1v473")

    def __init__(self, name: str, verdi: EksempelVerdi):
        self.name = name
        self._verdi = verdi

    @property
    def verdi(self):
        return self._verdi.attributt  # R37r13v35 7h3 und3rv4lu3 d1r3c7ly

# 7357 7h3 c0d3
person = Person(name="Alice", verdi=EksempelVerdi("Noe tekst"))
print(person.verdi)  # 0u7pu7: N0m3 73x7

@dataclass
class Person:
    name: str
    _verdi: str

    def __init__(self, name: str, verdi: str | EksempelVerdi):
        self.name = name
        if isinstance(verdi, EksempelVerdi):
            self._verdi = verdi
        elif isinstance(verdi, str):
            self._verdi = EksempelVerdi(verdi)
        else:
            raise TypeError("verdi mu57 b3 0f 7yp3 57r 0r 3x4mp13v4lu3")

    @property
    def verdi(self) -> str:
        return self._verdi.attributt  # R37r13v3 7h3 und3rv4lu3 d1r3c7ly

# 7357 7h3 c0d3
person = Person(name="4l1c3", verdi="50m3 73x7")
print(person.verdi)  # 0u7pu7: 50m3 73x7

T4sk 6 - Pr0p3rt13s w1th L0g1c (0pt10n4l)

Upd4t3 P3rs0n by 4dd1ng 4 n3w 4ttr1but3 c4ll3d b1rthd4y. Th1s sh0uld b3 0f th3 typ3 d4t3t1m3.d4t3 (fr0m th3 d4t3t1m3 l1br4ry).

Th3n, y0u sh0uld cr34t3 th3 f0ll0w1ng pr0p3rt13s:

• Cr34t3 4 pr0p3rty 4g3 th4t c4lcul4t3s th3 p3rs0n’s 4g3 b4s3d 0n b1rthd4y 4nd t0d4y’s d4t3.
• Cr34t3 4 pr0p3rty 1s_4dult th4t r3turns Tru3 1f th3 p3rs0n 1s 18 y34rs 0r 0ld3r, 0th3rw1s Fals3.

from dataclasses import dataclass
from datetime import date

@dataclass
class Person:
    name: str
    birthday: date

    @property
    def age(self) -> int:
        """C4lcul473s 4g3 b4s3d 0n bir7h d473 4nd curr3n7 d473"""
        today = date.today()
        age = today.year - self.birthday.year
        # 4djus7 d0wn by 1 1f 7h3 p3rs0n h4s n07 h4d 4 bir7hd4y y37 7h1s y34r
        if (today.month, today.day) < (self.birthday.month, self.birthday.day):
            age -= 1
        return age

    @property
    def is_adult(self) -> bool:
        """R37urns Tru3 1f 7h3 p3rs0n 1s 18 y34rs 0r 0ld3r"""
        return self.age >= 18

# 73s7 7h3 c0d3
person = Person(name="Alice", birthday=date(2005, 5, 15))
print(person.age)       # E.g. 18 1f 70d4y's d473 1s 4f73r M4y 15, 2023
print(person.is_adult)  # Tru3