动态函数变量名称

Question

How can I call python functions using dynamic variable names? This is an example:

class test(object):
    def __init__(self):
        self.a, self.b, self.c = 1, 2 ,3
    def __str__(self):
        return "a: " + str(self.a) + \
                          ", b: " + str(self.b) + \
                          ", c:" + str(self.c)       
    def inc_a(self):
        self.a += 1                          

t1 = test()
print(t1)
t1.inc_a() # this is what I DON'T want, individual increment functions
print(t1)

# I would like a inc that works like this:
# t1.inc(a) --> increase a by 1
# t1.inc(b) --> increase b by 1
# t1.inc(c) --> increase c by 1
# print(t1) 

Thx&kind regards

Answer 1

You can simply do it like this, using exec :

class test(object):
    def __init__(self):
        self.a, self.b, self.c = 1, 2 ,3
    def __str__(self):
        return "a: " + str(self.a) + \
                          ", b: " + str(self.b) + \
                          ", c:" + str(self.c)       
    def inc(self, v):
        exec("self.%s += 1" % (v))

OUTPUT

>>> t= test()
>>> print(t)
a: 1, b: 2, c:3
>>> t.inc('a')
>>> print(t)
a: 2, b: 2, c:3
>>> t.inc('b')
>>> print(t)
a: 2, b: 3, c:3
>>> t.inc('c')
>>> print(t)
a: 2, b: 3, c:4

However it would be better in your case to use setattr along with getattr since you're trying to set values for class variables, so your inc method will look something like this:

def inc(self, v):
    setattr(self, v, getattr(self, v)+1)

Output : same as above.