Hướng dẫn python string concatenation vs fstring - nối chuỗi python vs fstring

Hiệu suất khôn ngoan, tôi đã mong đợi chuỗi định dạng theo nghĩa đen sẽ nhanh hơn đáng kể so với cách ghép chuỗi tuy nhiên tôi đã bị sốc khi thấy đây không phải là trường hợp.

Tôi đã sử dụng mô -đun

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

from timeit import timeit
import matplotlib.pyplot as plt
n = 1000000000

setup = """\
a = 'a'*{str_len}
b = 'b'*{str_len}
"""

fstr_stmt = """\
f'{a}{b}'
"""

concat_stmt = """\
a+b
"""

str_lens = [10, 100, 1000, 10000, 100000, 1000000]
fstr_t = []
concat_t = []
for str_len in str_lens:
    n_iters = n//str_len
    fstr_t.append(timeit(setup=setup.format(str_len=str_len), stmt=fstr_stmt, number=n_iters)/n_iters)
    concat_t.append(timeit(setup=setup.format(str_len=str_len), stmt=concat_stmt, number=n_iters)/n_iters)
    ratio = fstr_t[-1]/concat_t[-1]
    print(f"For two strings of length {str_len:7d}, concatenation is {ratio:.5f} times faster than f-strings")
plt.plot(str_lens, fstr_t, "r*-")
plt.plot(str_lens, concat_t, "c*-")
plt.xscale("log")
plt.yscale("log")
plt.xlabel("String length (log scale)")
plt.ylabel("Seconds per iteration (log scale)")
plt.grid()
plt.show()

Đầu ra bảng điều khiển:

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

Và cốt truyện:

Tóm tắt: Sử dụng toán tử nối chuỗi nhanh hơn một chút so với việc sử dụng các chuỗi chữ số định dạng. Trừ khi bạn đang thực hiện hàng trăm ngàn lần ghép chuỗi và cần chúng được thực hiện rất nhanh, việc thực hiện được chọn không có khả năng tạo ra sự khác biệt. Using the string concatenation operator is slightly faster than using format string literals. Unless you are performing many hundreds of thousands of string concatenations and need them done very quickly, the implementation chosen is unlikely to make a difference.

Từ quan điểm dễ đọc, các chữ F-String có tính thẩm mỹ hơn và dễ đọc hơn so với nối dây. Ngoài ra, vì câu trả lời từ Daniel chỉ ra, các chuỗi F có thể xử lý các đầu vào của các loại khác nhau trong khi sử dụng

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

EDIT: Như Chepner chỉ ra trong nhận xét của họ, sử dụng F-Strings hiệu quả hơn khi có hơn hai chuỗi. Ví dụ: thêm một biến khác,

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For three strings of length      10, concatenation is 0.77931 times faster than f-strings
For three strings of length     100, concatenation is 0.67699 times faster than f-strings
For three strings of length    1000, concatenation is 0.60220 times faster than f-strings
For three strings of length   10000, concatenation is 1.27484 times faster than f-strings
For three strings of length  100000, concatenation is 0.98911 times faster than f-strings
For three strings of length 1000000, concatenation is 0.60201 times faster than f-strings

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Hãy nói về cách xây dựng các chuỗi lớn hơn từ các chuỗi nhỏ hơn trong Python. Hai phương pháp để thực hiện điều này là nối chuỗi và nội suy chuỗi.string concatenation and string interpolation.

Kết hợp chuỗi

Chúng tôi đã có một chuỗi đại diện cho một tên

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

>>> name = "Trey"
>>> message = "My name is " + name
>>> message
'My name is Trey'

Điều này được gọi là nối chuỗi. Từ nối về cơ bản là một từ lạ mắt để dán mọi thứ lại với nhau. Vì vậy, khi chúng tôi kết nối hai chuỗi, chúng tôi đang dán chúng lại với nhau bằng cách sử dụng dấu

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

Bây giờ, kết hợp chuỗi là tuyệt vời, nhưng đôi khi nó có thể có một chút khó sử dụng.

Đây là một ví dụ dài hơn nhiều về sự kết hợp chuỗi:

>>> "My name is " + name + " which has " + len(name) + " characters."

Thật dễ dàng để làm lỗi chính tả, trong khi bạn đang sử dụng kết nối chuỗi vì bạn đã có báo giá và cộng tất cả các xen kẽ giữa nhau. Cuối cùng chúng tôi đã không tạo một lỗi đánh máy ở trên, nhưng chúng tôi có lỗi trong mã của chúng tôi.

>>> "My name is " + name + " which has " + len(name) + " characters."
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can only concatenate str (not "int") to str

Gọi

For three strings of length      10, concatenation is 0.77931 times faster than f-strings
For three strings of length     100, concatenation is 0.67699 times faster than f-strings
For three strings of length    1000, concatenation is 0.60220 times faster than f-strings
For three strings of length   10000, concatenation is 1.27484 times faster than f-strings
For three strings of length  100000, concatenation is 0.98911 times faster than f-strings
For three strings of length 1000000, concatenation is 0.60201 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

Vì vậy, chúng ta cần chuyển đổi

For three strings of length      10, concatenation is 0.77931 times faster than f-strings
For three strings of length     100, concatenation is 0.67699 times faster than f-strings
For three strings of length    1000, concatenation is 0.60220 times faster than f-strings
For three strings of length   10000, concatenation is 1.27484 times faster than f-strings
For three strings of length  100000, concatenation is 0.98911 times faster than f-strings
For three strings of length 1000000, concatenation is 0.60201 times faster than f-strings

>>> "My name is " + name + " which has " + str(len(name)) + " characters."
'My name is Trey which has 4 characters.'

Mã mà chúng tôi đã kết thúc là mã Python khá dễ đọc, nhưng nó có thể dễ đọc hơn.

Chuỗi nội suy

Một cách khác để xây dựng một chuỗi lớn hơn từ các chuỗi nhỏ hơn là nội suy chuỗi. Trong Python, điều này thường được gọi là định dạng chuỗi. Để thực hiện định dạng chuỗi, chúng ta có thể sử dụng chuỗi F.string interpolation. In Python this is often called string formatting. To do string formatting, we can use an f-string.

Một chuỗi F không phải là công cụ duy nhất cho điều này (phương thức chuỗi ____27 là phương pháp khác), nhưng nó là công cụ phổ biến nhất bạn sẽ thấy:

>>> f"My name is {name} which has {len(name)} characters."
'My name is Trey which has 4 characters.'

Một chuỗi F là một chuỗi có "F" ở phía trước của nó. Không có "F" đó ở phía trước của nó, nó chỉ là một chuỗi thông thường:

>>> "My name is {name} which has {len(name)} characters."
'My name is {name} which has {len(name)} characters.'

Chỉ đơn giản bằng cách đặt F F ngay trước chuỗi, bất kể chúng tôi sử dụng dấu ngoặc kép

For three strings of length      10, concatenation is 0.77931 times faster than f-strings
For three strings of length     100, concatenation is 0.67699 times faster than f-strings
For three strings of length    1000, concatenation is 0.60220 times faster than f-strings
For three strings of length   10000, concatenation is 1.27484 times faster than f-strings
For three strings of length  100000, concatenation is 0.98911 times faster than f-strings
For three strings of length 1000000, concatenation is 0.60201 times faster than f-strings

For three strings of length      10, concatenation is 0.77931 times faster than f-strings
For three strings of length     100, concatenation is 0.67699 times faster than f-strings
For three strings of length    1000, concatenation is 0.60220 times faster than f-strings
For three strings of length   10000, concatenation is 1.27484 times faster than f-strings
For three strings of length  100000, concatenation is 0.98911 times faster than f-strings
For three strings of length 1000000, concatenation is 0.60201 times faster than f-strings

>>> name = "Trey"
>>> message = "My name is " + name
>>> message
'My name is Trey'

For three strings of length      10, concatenation is 0.77931 times faster than f-strings
For three strings of length     100, concatenation is 0.67699 times faster than f-strings
For three strings of length    1000, concatenation is 0.60220 times faster than f-strings
For three strings of length   10000, concatenation is 1.27484 times faster than f-strings
For three strings of length  100000, concatenation is 0.98911 times faster than f-strings
For three strings of length 1000000, concatenation is 0.60201 times faster than f-strings

>>> f"My name is {name} which has {len(name)} characters."
'My name is Trey which has 4 characters.'

Bản tóm tắt

Bạn có thể nghĩ về sự kết hợp chuỗi như dán dây lại với nhau. Và, bạn có thể nghĩ về phép nội suy chuỗi mà không cần các chuỗi tiêm bên trong các chuỗi khác.string interpolation without strings as injecting strings inside of other strings.

Hai cách để xây dựng một chuỗi lớn hơn từ các chuỗi nhỏ hơn là sự kết hợp chuỗi (sử dụng ký hiệu

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

For two strings of length      10, concatenation is 1.06938 times faster than f-strings
For two strings of length     100, concatenation is 1.14887 times faster than f-strings
For two strings of length    1000, concatenation is 1.13994 times faster than f-strings
For two strings of length   10000, concatenation is 1.26934 times faster than f-strings
For two strings of length  100000, concatenation is 1.21585 times faster than f-strings
For two strings of length 1000000, concatenation is 1.01816 times faster than f-strings

Cách tốt nhất để nối các chuỗi trong Python là gì?

Sự khác biệt giữa nối chuỗi và nội suy là gì?

Chuỗi F có nhanh hơn Concatenate không?

Những lợi ích của việc sử dụng phương thức .Format thay vì nối chuỗi trong Python là gì?