如何使用循环创建变量？

Question

所以，我想从我正在循环的列表列表中务实地创建 class 个实例。怎么做？

class foo:
   def __init__(self, first, second):
      self.first = first
      self.second = second

my_list = [[a_0, a_1, a_2], [b_0, b_1, b_2], [c_0, c_1, c_2]]
i = 1
instance_name = instance_
for list in my_list:
   x = instance_name + str(i)
   x = foo(list[0], list[2])
   i += 1

我知道循环中的第二个 x 是完全错误的。但是我需要能够在将来使用 x 的值调用我的实例。有帮助吗？

Answer 1

只需使用列表理解并在该列表中构造实例：

class Foo:

    def __init__(self, first, second):
        self.first = first
        self.second = second


# List of parameters to pass to Foo
args_list = [(1, 2), (3, 4), (5, 6)]

# Add an instance of Foo(first num, second num) to the instances list
# for every set of arguments above
instances = [Foo(value[0], value[1]) for value in args_list]


# Print out each of the instances values
for instance in instances:
    print(instance.first, instance.second)
# prints:
# 1 2
# 3 4
# 5 6

# OR you can call an individual instance like so

print(instances[0].first, instances[0].second)
# prints:
# 1 2

Answer 2

正如@roganjosh 的评论所说，变量 x 的数据正在被覆盖，因此如果您想创建变量，请使用 locals() 但这不是一个好的做法。最好用字典来存储实例，即

class foo:
    def __init__(self, first, second):
        self.first = first
        self.second = second

a_0,a_1,a_2 = 1,2,3
b_0,b_1,b_2 = 4,5,6
c_0,c_1,c_2 = 7,8,9

my_list = [[a_0, a_1, a_2], [b_0, b_1, b_2], [c_0, c_1, c_2]]

for i,li in enumerate(my_list):
    locals()['instance_{}'.format(i+1)] = foo(li[0], li[2])
# instance_1.first 
# 1
# instance_3.first
# 7

字典方法是：

x = {'instance_{}'.format(i+1): foo(li[0], li[2]) for i,li in enumerate(my_list) }

#x['instance_1'].first
#1

如何使用循环创建变量？

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python-2.7