在定义之前使用名称 [英] using names before they're defined
问题描述
我有问题。我正在编写一个模拟程序，其中包含许多
机械组件，表示为对象。当我创建实例
的对象时，我需要引用（链接）每个对象
上游和下游，即
供应=供应（）
压缩机=压缩机（下游=燃烧室，上游=供应）
燃烧器=燃烧器（下游=涡轮，上游=压缩机）
等
这个问题是我之前引用''燃烧器''
创建。如果我交换第2行和第3行我得到同样的问题
（压缩机在创建之前被引用）。
aargh !!!有关解决这个问题的任何想法吗？
Dave
I have a problem. I''m writing a simulation program with a number of
mechanical components represented as objects. When I create instances
of objects, I need to reference (link) each object to the objects
upstream and downstream of it, i.e.
supply = supply()
compressor = compressor(downstream=combustor, upstream=supply)
combuster = combuster(downstream=turbine, upstream=compressor)
etc.
the problem with this is that I reference ''combustor'' before is it
created. If I swap the 2nd and 3rd lines I get the same problem
(compressor is referenced before creation).
aargh!!! any ideas on getting around this?
Dave
推荐答案
daveho ... @ f2s.com写道：
daveho...@f2s.com wrote:
我有问题。我正在编写一个模拟程序，其中包含许多
机械组件，表示为对象。当我创建实例
的对象时，我需要引用（链接）每个对象
上游和下游，即
供应=供应（）
压缩机=压缩机（下游=燃烧室，上游=供应）
燃烧器=燃烧器（下游=涡轮，上游=压缩机）
等
这个问题是我之前引用''燃烧器''
创建。如果我换掉第2行和第3行我会得到同样的问题
（压缩器在创建之前被引用）。
aargh !!!有关解决此问题的任何想法吗？
Dave
I have a problem. I''m writing a simulation program with a number of
mechanical components represented as objects. When I create instances
of objects, I need to reference (link) each object to the objects
upstream and downstream of it, i.e.
supply = supply()
compressor = compressor(downstream=combustor, upstream=supply)
combuster = combuster(downstream=turbine, upstream=compressor)
etc.
the problem with this is that I reference ''combustor'' before is it
created. If I swap the 2nd and 3rd lines I get the same problem
(compressor is referenced before creation).
aargh!!! any ideas on getting around this?
Dave
在您的代码顶部，您可以放置：
供应=无
压缩机=无
燃烧器=无
涡轮机=无
但是，安排你的代码可能会更好：
supply = Supply（）
compressor = Compressor（）
combuster = Combuster（）
turbine = Turbine（）
compressor.setStreams（down = combuster，up = supply）
combuster .setStreams（down = turb，up = compressor）
流是否相互反映？也就是说，如果supply.down是压缩机的b $ b $，那么压缩机供应量是多少？在这种情况下你可能想要
做类似的事情：
class Component（）：
upstream =没有
下游=无
def setUpstream（self，c）：
self.upstream = c
if c.downstream！= self：
c.setDownstream（self）
def setDownstream（self，c）：
self.downstream = c
如果c.upstream！= self：
c.setUpstream（self）
类供应（组件）：
通过
等
Iain
At the top of your code you could put:
supply = None
compressor = None
combuster = None
turbine = None
It might be better, though, to arrange your code like:
supply = Supply()
compressor = Compressor()
combuster = Combuster()
turbine = Turbine()
compressor.setStreams(down=combuster, up=supply)
combuster.setStreams(down=turbine, up=compressor)
Do the streams reflect each other? That is, if supply.down is
compressor, is compressor.up supply? In that case you probably want to
do something like:
class Component():
upstream = None
downstream = None
def setUpstream(self, c):
self.upstream = c
if c.downstream != self:
c.setDownstream(self)
def setDownstream(self, c):
self.downstream = c
if c.upstream != self:
c.setUpstream(self)
class Supply(Component):
pass
etc.
Iain
da*******@f2s.com 写道：
da*******@f2s.com wrote:
我有问题。我正在编写一个模拟程序，其中包含许多
机械组件，表示为对象。当我创建实例
的对象时，我需要引用（链接）每个对象
上游和下游，即
供应=供应（）
压缩机=压缩机（下游=燃烧室，上游=供应）
燃烧器=燃烧器（下游=涡轮，上游=压缩机）
等
这个问题是我之前引用''燃烧器''
创建。如果我换掉第2行和第3行我会得到同样的问题
（压缩器在创建之前被引用）。
aargh !!!有关解决这个问题的任何想法吗？
I have a problem. I''m writing a simulation program with a number of
mechanical components represented as objects. When I create instances
of objects, I need to reference (link) each object to the objects
upstream and downstream of it, i.e.
supply = supply()
compressor = compressor(downstream=combustor, upstream=supply)
combuster = combuster(downstream=turbine, upstream=compressor)
etc.
the problem with this is that I reference ''combustor'' before is it
created. If I swap the 2nd and 3rd lines I get the same problem
(compressor is referenced before creation).
aargh!!! any ideas on getting around this?
是的。你正在构建一个通用的数据结构，所以你不应该试图将各个对象存储在这样的变量中。你需要一个适合你问题的
数据结构。
例如，你可以考虑将它们存储在一个列表中，这样你就有了
components = [supply（），compressor（），combuster（）]
然后components [n]是组件的上游[n- 1]和下游
组件[n + 1]。
简而言之，您对数据表示的思考可能需要成为一个
稍微复杂一点。
问候
Steve
-
Steve Holden + 44 150 684 7255 +1 800 494 3119
Holden Web LLC / Ltd http： //www.holdenweb.com
Skype：holdenweb http： //holdenweb.blogspot.com
最近的Ramblings http://del.icio.us/steve。 holden
Yes. You are building a generic data structure, so you shouldn''t really
be trying to store individual objects in variables like that. You need a
data structure that''s appropriate to your problem.
For example, you could consider storing them in a list, so you have
components = [supply(), compressor(), combuster()]
Then components[n] is upstream of components[n-1] and downstream of
components[n+1].
In short, your thinking about data representation might need to become a
little more sophisticated.
regards
Steve
--
Steve Holden +44 150 684 7255 +1 800 494 3119
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://holdenweb.blogspot.com
Recent Ramblings http://del.icio.us/steve.holden
类似的东西：
供应=供应（）
压缩机=压缩机（供应）
combuster = combuster（压缩机）
compressor.append（combuster）
turbine = turbine（燃烧器）
combuster.append（涡轮机）
-Larry Bates
da ******* @ f2s.com 写道：
What about something like:
supply = supply()
compressor = compressor(supply)
combuster = combuster(compressor)
compressor.append(combuster)
turbine = turbine(combuster)
combuster.append(turbine)
-Larry Bates
da*******@f2s.com wrote:
我有问题。我正在编写一个模拟程序，其中包含许多
机械组件，表示为对象。当我创建实例
的对象时，我需要引用（链接）每个对象
上游和下游，即
供应=供应（）
压缩机=压缩机（下游=燃烧室，上游=供应）
燃烧器=燃烧器（下游=涡轮，上游=压缩机）
等
这个问题是我之前引用''燃烧器''
创建。如果我换掉第2行和第3行我会得到同样的问题
（压缩器在创建之前被引用）。
aargh !!!有关解决这个问题的任何想法吗？
Dave
I have a problem. I''m writing a simulation program with a number of
mechanical components represented as objects. When I create instances
of objects, I need to reference (link) each object to the objects
upstream and downstream of it, i.e.
supply = supply()
compressor = compressor(downstream=combustor, upstream=supply)
combuster = combuster(downstream=turbine, upstream=compressor)
etc.
the problem with this is that I reference ''combustor'' before is it
created. If I swap the 2nd and 3rd lines I get the same problem
(compressor is referenced before creation).
aargh!!! any ideas on getting around this?
Dave
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