python - 如何在没有++ 运算符的情况下更紧凑地编写此语句？

Question

这是我想写的:

groups[m][n] = groups[m - 1][n] or ++gid

这是我要写的内容:

g = groups[m - 1][n]
if g:
    groups[m,n] = g
else:
    gid += 1
    groups[m][n] = gid

是否没有更紧凑的方式在 Python 中编写它，仅仅因为它缺少 ++ 运算符？

<小时/>

我正在研究的方法的更大样本:

groups = [[0] * self.columns] * self.rows
gid = 0
for m in xrange(self.rows):
    for n in xrange(self.columns):
        stone = self[m, n]
        if stone == self[m - 1, n]:
            if groups[m - 1][n]:
                groups[m][n] = groups[m - 1][n]
            else:
                gid += 1
                groups[m][n] = gid
        elif stone == self[m, n - 1]:
            if groups[m][n - 1]:
                groups[m][n] = groups[m][n - 1]
            else:
                gid += 1
                groups[m][n] = gid

我认为当我必须像这样把它吹出来时，阅读起来会困难得多，而且我正在评估 m-1 两次......我不知道如何压缩它不过。

<小时/>

这是我想到的:

我围绕 int 创建了一个包装类:

class Int(object):
    def __init__(self, i):
        self.i = i

    def pre(self, a=1):
        self.i += a
        return Int(self.i)

    def post(self, a=1):
        cpy = Int(self.i)
        self.i += a
        return cpy

    def __repr__(self):
        return str(self.i)

    def __nonzero__(self):
        return self.i != 0

可以这样使用:

def group_stones(self):
    groups = [[None for _ in xrange(self.cols)] for _ in xrange(self.rows)]
    gid = Int(0)
    for m in xrange(self.rows):
        for n in xrange(self.cols):
            stone = self[m, n]
            if stone == self[m - 1, n]:
                groups[m][n] = groups[m - 1][n] or gid.pre()
            elif stone == self[m, n - 1]:
                groups[m][n] = groups[m][n - 1] or gid.pre()
            else:
                groups[m][n] = gid.pre()

就像我在其他语言中所做的那样。

Answer 1

gid = [0] # list - mutable object

def incremented(gid):
    gid[0] += 1
    return gid[0]

groups[m][n] = groups[m - 1][n] or incremented(gid)

您可以向 Int 类添加一些“魔法”:

class C(object):
    ...
    def __add__(self, other):
        self.i += other
        return self.__class__(self.i)
    def __radd__(self, other):
        cpy = self.__class__(self.i)
        self.i += other
        return cpy

>>> print Int(2) + 1 # pre
3
>>> i = Int(2)
>>> print 1 + i # post
2
>>> print i
3