Скорее всего уже слышали, что складывать строки через + это плохая практика. Падение производительности, и всё такое. Без лишних слов, давайте измерять:
from timeit import timeit
def t1():
# складываем 10 строк через + из переменной
t = 'text'
for _ in range(1000):
s = t + t + t + t + t + t + t + t + t
def t2():
# склеиваем список строк через метод join
arr = ['text'] * 10
for _ in range(1000):
s = ''.join(arr)
def t3():
# складываем через + но не из переменной а непосредственно инлайн объекты
for _ in range(1000):
s = 'text' + 'text' + 'text' + ... # всего 10 раз
Теперь каждую строку склейки запустим по 10М раз
>>> timeit(t1, number=10000)
0.21951690399964718
>>> timeit(t2, number=10000)
1.4978306379998685
>>> timeit(t3, number=10000)
0.2213820789993406
Хм, а нам говорили что через "+" это плохо и медленно ))) 😁
Тут стоит учитывать, что речь идёт о склейке множества длинных строк.
Давайте изменим условия:
def t4():
t = 'text'*100
for _ in range(1000):
s = t + t + t + t + t + t + t + t + t
def t5():
arr = ['text'*100] * 10
for _ in range(1000):
s = ''.join(arr)
def t6():
for _ in range(1000):
s = 'text'*100 + 'text'*100 + ... # всего 10 раз
>>> timeit(t4, number=10000)
12.795130728000004
>>> timeit(t5, number=10000)
2.642637542999182
>>> timeit(t6, number=10000)
0.2184546610005782
Вот, уже другой разговор, сразу видна разница, в среднем в 6 раз. Но погодите, почему последний тест t6() по скорости такой же как и t3()? Ведь строки теперь в 100 раз длиннее!
Это вопросы оптимизации кода, какие простые изменения ускоряют или замедляют выполнение программы. Мы столкнулись с примером обхода обращения к переменной. Например, именно так работает директива #define в С++, во время компиляции подставляя значение переменной вместо ссылки на неё.
В Python это тоже работает, но часто ли вы сможете встретить такой способ работы со строками? К сожалению, способ почти только теоретический.
В целом, тесты показали то, что мы хотели. Делаем выводы самостоятельно.
Полный листинг 🌍
#tricks
😄Pretty
➖➖➖➖➖➖
🔘Pretty as an adjective means 'attractive, especially when talking about girls or women'.
Margo always tells her daughter that she's pretty.Margo always tells her daughter that she's pretty.
🔜Jacob's mum is really pretty.
🔘Pretty is also used to talk about things that are 'pleasant to look at in a delicate or charming way'. While this is often connected to females, it can also be used to describe something like 'a view'.
🔜There's a very pretty view at the top of that hill.
🔜My friend moved out of the city and bought a pretty cottage in the countryside.
🔘As an adverb, pretty can be an informal way of saying 'quite' or 'rather'.
🔜The house was built recently, it's pretty new.
🔜I enjoyed that film, it was pretty good.
🔘We can also use pretty to give emphasis.
🔜We went to bed at 2am, so we were pretty tired.
🔜I'm pretty angry right now, so don't talk to me.
#Pretty👨🏫@America
➖➖➖➖➖➖➖➖➖➖➖➖
🆕 Crypto News @Money
😁 Crypto Game @Egame
🇺🇸 US News @America
🇯🇵 Japan News @Japan
🇦🇪 UAE News @Dubai
▶️ Popular Movies @Videos
😜 Best Funny Video @Funnys
😄Pretty
➖➖➖➖➖➖
🔘Pretty as an adjective means 'attractive, especially when talking about girls or women'.
Margo always tells her daughter that she's pretty.Margo always tells her daughter that she's pretty.
🔜Jacob's mum is really pretty.
🔘Pretty is also used to talk about things that are 'pleasant to look at in a delicate or charming way'. While this is often connected to females, it can also be used to describe something like 'a view'.
🔜There's a very pretty view at the top of that hill.
🔜My friend moved out of the city and bought a pretty cottage in the countryside.
🔘As an adverb, pretty can be an informal way of saying 'quite' or 'rather'.
🔜The house was built recently, it's pretty new.
🔜I enjoyed that film, it was pretty good.
🔘We can also use pretty to give emphasis.
🔜We went to bed at 2am, so we were pretty tired.
🔜I'm pretty angry right now, so don't talk to me.
#Pretty👨🏫@America
➖➖➖➖➖➖➖➖➖➖➖➖
🆕 Crypto News @Money
😁 Crypto Game @Egame
🇺🇸 US News @America
🇯🇵 Japan News @Japan
🇦🇪 UAE News @Dubai
▶️ Popular Movies @Videos
😜 Best Funny Video @Funnys
http://www.enlistq.com/10-python-idioms-to-help-you-improve-your-code/
If you have ever tried to learn a new language (not a programming language), you know that we always think in our native language before we translate it to the new language. This can lead to you forming some sentences that don’t make sense in the new language but are perfectly normal in your native language. For example, in a lot of languages, you ‘open’ an electronic gadget such as fan, AC or cell phone. When you say that in English, it means to literally open the gadget instead of turning it on.
The same is true for programming languages. As we pick up new languages, such as #python, we are using our prior knowledge of programming in another language (q, java, c++ etc) and translating that to python. Many times, your code will work but it won’t be ‘#pretty’ or #fast. In python terms, your code won’t be ‘#pythonic’.