python - 嵌套 for 循环以列出具有不同 "if"条件的理解

Question

我正在尝试将此嵌套循环转换为列表推导式，但我不确定是否可行，因为“tmp”列表中的项目可能有不同的值。这是最好的方法吗？谢谢!

final = []
for a in range(-13, 1):
    for b in range(0,4):
        for c in range(6, 49):
            for d in range(48, 94):
                tmp = [0 for i in range(100)]
                for i in range(100):
                    if raw_x[i] >= b and raw_y[i] >= d:
                        tmp [i] = -1
                    if raw_x[i] <= a and raw_y[i] <= c:
                        tmp [i] = 1
                final.append(tmp)

Answer 1

嵌套推导的可读性不是很好

一个简单的

[something for something in container if something > 9]

很棒，但嵌套的常常令人困惑

你可以简单地将循环移动到一个生成器函数中——它仍然是可读的并且允许惰性迭代

def no_idea_what_this_represents():
    for a in range(-13, 1):
        for b in range(0,4):
            for c in range(6, 49):
                for d in range(48, 94):
                    tmp = [0 for i in range(100)]
                    for i in range(100):
                        if raw_x[i] >= b and raw_y[i] >= d:
                            tmp [i] = -1
                        if raw_x[i] <= a and raw_y[i] <= c:
                            tmp [i] = 1
                    yield tmp

final = [signs for signs in no_idea_what_this_represents()]

编辑:只是一个自以为是的附录——这样就可以命名复杂的嵌套循环(出于显而易见的原因，我将其命名为 no_idea_what_this_represents)但是当程序员看到

possible_views = [matrix for matrix in camera_matrices()]

他马上就知道这是什么意思了

possible_views = [device.matrix 
                  for devices in itertools.chain(connected_devices(), buffered_devices()
                  for device in devices
                  if device.type=='camera']

让程序员读了很多行并且不清楚发生了什么