Ko te Python me nga tikanga matatau, nga mahi dunder mo te pai ake o nga kaupapa

Ko te Python he reo hötaka tino pai, me te whakaatu mai GitHub, ko te reo tuarua tino rongonui i te tau 2022.

Ko nga painga tino pai o Python ko te hapori nui o nga kaiwhakatakoto kaupapa.

Te ahua nei kei a Python tetahi kete mo tetahi keehi whakamahi.

I roto i te ao nui o te kaupapa Python, he huinga o nga ahuatanga kaore e kitea e te hunga hou, engari he mea nui ki te puunaha hauropi o te reo.

Ko nga tikanga makutu he huinga o nga tikanga o muadefinites i roto i te Python e whakarato ana i nga ahuatanga syntactic motuhake. He ngawari te mohio ki a raatau ma o raatau tohu takirua i te timatanga me te mutunga, penei __init__, __call__, __len__ … etc.

Nga Tikanga Maamaa

Ka taea e nga tikanga makutu te ahua o nga mea ritenga ki nga momo Python kua hangaia.

I roto i tenei tuhinga, ka arotahi tatou ki nga mahi kaha o te dunder. Ka tuhurahia e maatau te kaupapa me te korero mo te whakamahinga.

Ahakoa he tauhou a Python koe, he kaiwhakatakoto kaupapa mohio ranei, e whai ana tenei tuhinga ki te whakarato ki a koe i te maaramatanga matawhānui mo nga mahi a Dunder, kia pai ake ai to wheako tohu Python.

Kia maumahara, ko te makutu o Python ehara i te mea ko te ngawari me te ngawari, engari ko nga ahuatanga kaha penei i nga mahi a Dunder.

__init__

Pea ko te tino mahi dunder taketake o te katoa. Koinei te tikanga makutu e karanga aunoatia ana e Python i nga wa katoa ka waihangahia e matou (i runga ranei i te ingoa e kii ana, arawhiti) he ahanoa hou.__init__

Piha karaehe:
    def __init__(whaiaro, rahi, toppings):
        whaiaro.rahi = rahi
        whaiaro.toppings = toppings

# Inaianei me hanga he pizza
my_pizza = Pizza('nui', ['pepperoni', 'harore'])

tā(my_pizza.size) # Ka tā tēnei: ​​nui
tā(my_pizza.toppings) # Ka tā: ['pepperoni', 'harore']

I tenei tauira, ka hangaia he karaehe e kiia nei ko Pizza. I whakaturia e matou ta matou mahi __init__ ki te whakauru i nga tawhā ka tohua i te wa arawhiti, ka whakatauhia hei taonga mo a maatau mea ritenga.

I konei, ka whakamahia hei tohu i te tauira o te karaehe. Na ka tuhi tatou self.size = rahi, kei te kii tatou, "Hey, he rahi huanga to tenei ahanoa pizza size, a ko taku hiahia kia rite ki te rahi i hoatu e ahau i te wa i hanga ai e au te ahanoa”.

__str__ me __repr__

__Str__

Koinei te tikanga makutu a Python e taea ai e tatou definish he whakaahuatanga mo a maatau mea ritenga.

Ina ta koe i tetahi mea, ka huri ranei ki te aho ma te whakamahi str(), Tirohia te Python mena kei a koe defiKua puta mai he tikanga __str__ mo te akomanga o taua mea.

Ki te pera, whakamahia taua tikanga hei huri i te ahanoa ki te aho.

Ka taea e tatou te whakawhānui atu i to tatou tauira Pizza ki te whakauru i tetahi mahi __str__ e whai ake nei:

Piha akomanga: def __init__(whaiaro, rahi, toppings): whaiaro.size = rahi self.toppings = toppings def __str__(self): whakahokia f"He {self.size} pizza with {', '.join(self.toppings )}" my_pizza = Pizza('nui', ['pepperoni', 'harore']) tā(my_pizza) # Ka tā tenei: He pizza nui me te pepperoni, harore

__repr__

Ko te mahi __str__ he tikanga opaki mo te whakaahua i nga ahuatanga o tetahi mea. I tetahi atu taha, ka whakamahia te __repr__ ki te whakarato i tetahi whakaahuatanga okawa ake, taipitopito me te maamaa mo te ahanoa ritenga.

Ki te waea koe repr() i runga i tetahi ahanoa ka pato noa ranei koe i te ingoa ahanoa ki te papatohu, ka rapua e Python tetahi tikanga __repr__.

Se __str__ ehara i te mea defii te ahiahi, ka whakamahia e Python __repr__ hei tārua ina ngana ana ki te tā i te ahanoa ki te huri ranei ki te aho. No reira he whakaaro pai tonu defiwhakaoti i te iti rawa __repr__, ahakoa kaore koe defipai __str__.

Anei me pehea e taea ai e matou defimutu __repr__ mo ta maatau tauira pizza:

Piha karaehe:
    def __init__(whaiaro, rahi, toppings):
        whaiaro.rahi = rahi
        whaiaro.toppings = toppings

    def __repr__(whaiaro):
        whakahokia f"Pizza('{self.size}', {self.toppings})"

my_pizza = Pizza('nui', ['pepperoni', 'harore'])
tā(repr(my_pizza)) # Ka tā tēnei: ​​Pizza('nui', ['pepperoni', 'harore'])

__repr__ ka hoatu he aho ki a koe ka taea e koe te whakahaere hei whakahau Python ki te hanga ano i te ahanoa pizza, engari __str__ ka hoatu ki a koe he whakaahuatanga tangata ake. Ko taku tumanako ka awhina koe ki te ngaungau i enei tikanga dunder kia pai ake!

__tāpiri__

I roto i te Python, e mohio ana tatou ka taea te taapiri i nga nama ma te whakamahi i te kaiwhakahaere +, rite 3 + 5.

Engari ka pehea mena ka hiahia taatau ki te taapiri i nga tauira o etahi mea ritenga?

Ko te mahi dunder __add__ ka taea e tatou te mahi pera. Ka homai e ia te kaha ki a tatou definish te whanonga o te kaiwhakahaere + i runga i a maatau taonga whaiaro.

I roto i te hiahia o te riterite, me whakaaro tatou e hiahia ana tatou defimutu te whanonga o + i runga i ta maatau tauira pizza. Me kii tatou ka taapirihia kia rua, neke atu ranei nga pizzas, ka whakakotahi aunoa i o ratou toppings katoa. Anei te ahua o te ahua:

Piha karaehe:
    def __init__(whaiaro, rahi, toppings):
        whaiaro.rahi = rahi
        whaiaro.toppings = toppings

    def __add__(whaiaro, atu):
        ki te kore he isinstance(etahi atu, Pizza):
            whakaarahia TypeError("Ka taea e koe anake te taapiri i tetahi atu Pizza!")
        new_toppings = whaiaro.toppings + other.toppings
        whakahokia Pizza(self.size, new_toppings)

# Me hanga e rua nga pizzas
pizza1 = Pizza('nui', ['pepperoni', 'harore'])
pizza2 = Pizza('nui', ['olive', 'pineaporo'])

# Na inaianei me "tapiri" ratou
whakakotahi_pizza = pizza1 + pizza2

tā(combined_pizza.toppings) # Ka tā tēnei: ​​['pepperoni', 'harore', 'olive', 'pineapple']

He rite ano ki te dunder __add__, ka taea hoki e tatou defiwhakaoti i etahi atu mahi tatau penei i __sub__ (ma te tangohanga ma te whakamahi i te kaiwhakahaere -) ā __mul__ (mo te whakarea ma te whakamahi i te kaiwhakahaere *).

__len__

Ma tenei tikanga dunder ka taea e taatau defioti te mahi len() me hoki mai mo a maatau mea kua whakaritea.

Ka whakamahia e Python len() ki te tiki i te roa, te rahi ranei o te hanganga raraunga penei i te rarangi, aho ranei.

I roto i te horopaki o to tatou tauira, ka taea e tatou te kii ko te "roa" o te pizza ko te maha o nga toppings kei a ia. Anei me pehea e taea ai e matou te whakatinana:

Piha karaehe:
    def __init__(whaiaro, rahi, toppings):
        whaiaro.rahi = rahi
        whaiaro.toppings = toppings

    def __len__(whaiaro):
        whakahokia len(self.toppings)

# Me hanga he pizza
my_pizza = Pizza('nui', ['pepperoni', 'harore', ' oriwa'])

tā(len(my_pizza)) # Ka tā tēnei: ​​3

I te tikanga __len__, ka whakahokia noa te roa o te rarangi toppings. Na, len(my_pizza) ka whakaatu mai e hia nga toppings kei runga my_pizza.

__tikanga__

Ko tenei tikanga dunder ka taea e nga mea te huri, ara, ka taea te whakamahi i roto i te mo te koropiko.

Ki te mahi i tenei, me maatau ano defiwhakaoti i te mahi __next__, Ka whakamahia tenei mo defiwhakamutua te whanonga e hoki mai ai te uara e whai ake nei i roto i te whitiwhitinga. Me tohu ano i te kaitahuri i runga i te mea kua kore he huānga o te raupapa. I te nuinga o te wa ka tutuki tenei ma te maka i tetahi tuunga StopIteration.

Mo ta maatau tauira pizza, me kii e hiahia ana matou ki te huri i nga toppings. Ka taea e taatau te whakarite i to maatau karaehe Pizza definendo a tikanga __iter__:

Piha karaehe:
    def __init__(whaiaro, rahi, toppings):
        whaiaro.rahi = rahi
        whaiaro.toppings = toppings

    def __iter__(whaiaro):
        whaiaro.n = 0
        hoki mai

    def __next__(whaiaro):
        if self.n < len(self.toppings):
            hua = self.toppings[self.n]
            whaiaro.n += 1
            hua whakahoki
        atu:
            whakaarahia StopIteration

# Me hanga he pizza
my_pizza = Pizza('nui', ['pepperoni', 'harore', ' oriwa'])

# Inaianei me huri ano
mo te tihi i taku_pizza:
    tā(topping)

I roto i tenei take, ka karanga te mo te koropiko __iter__, ka arawhiti i te porotiti (self.n) me te whakahoki ano i te mea pizza (self).

Na, ka karanga te mo te koropiko __next__ ki te tiki ia topping i roto i te huri.

Anei __next__ whakahokia nga mea kakara katoa, StopIteration ka maka he okotahi ka mohio te mo te karekau kua kore he toppings ka mutu te tukanga whitiwhiti.

Ercole Palmeri