將 for 循環轉換為單行循環以比較性能

Question

我正在比較執行兩個代碼塊所需的時間：

import time

start = time.time()
a = []
for x in range(10000):
    if x % 2 == 0:
        a.append(x)

finish = time.time()
print('stopwatch: ', finish - start)

但是當我將 for 循環變成單行時，我收到語法錯誤：

start = time.time()
a = [x if x % 2 == 0 for x in range(10000)]
finish = time.time()
print('stopwatch: ', finish - start)

我將如何為上面的 for 循環編寫一行代碼？

Answer 1

您應該檢查列表推導式的正確語法。 正確的方法：

a = [x for x in range(10000) if x % 2 == 0]

Answer 2

if在for x in range() ：

a = [x for x in range(10000) if x % 2 == 0]

Answer 3

你的 if 語句放錯了地方。

start = time.time()
a = [x for x in range(10000) if x % 2 == 0 ]
finish = time.time()
print('stopwatch: ', finish - start)