python pickle模块的简单使用笔记

Python pickle 模块提供了把对象序列化的方法，对象会被序列化成ASCII的字符串，可以保存到文件。unpickle则可以从文件或字符中反序列化成对象。如下的两个方法非常有用。pickle.dumps(obj[,protocol])Return the pickled representation of the object as a string, instead of writing it to a file.If the protocol parameter is omitted, protocol 0 is used. If protocol is specified as a negative value or HIGHEST_PROTOCOL, the highest protocol version will be used.Changed in version 2.3: The protocol parameter was added.pickle.loads(string)Read a pickled object hierarchy from a string. Characters in the string past the pickled object’s representation are ignored.我在使用wx时，wxGrid的GetCellValue方法只能返回字符串。但我希望它可以返回我定义的对象，于是我找到了pickle。我在类中重写__str__()方法，使用pickle来序列化这个对象。例子：

import pickle
class LineProperty:
def __init__(self, width=0, shape=0xFFFF, r=0, g=0, b=0, color=0):
self.width = width
self.shape = shape
self.r = r
self.g = g
self.b = b
self.color = color
#使用pickle 序列化
def __str__(self):
return pickle.dumps(self)

然后我在自己定义的wxGridTable中设置了这个数据，GridCellEditor中的重写的BeginEditor方法

class LineGridCellEditor(grd.PyGridCellEditor):
def Create(self, parent, id, evtHandler):
self._control = wx.Control(parent, id, wx.DefaultPosition, (100, 100))
self._parent = parent
self.SetControl(self._control)
        newEvt = wx._core.EvtHandler()
        if newEvt:
            self._control.PushEventHandler(newEvt)
        self.startValue = self.endValue = None
        self.m_canvas = linecanvas.MyLineCanvas(self._control)
    def OnClick(self, evt):
        pass
    def Clone(self):
        return LineGridCellEditor()
    def BeginEdit(self, row, col, grid):
        self.startValue = grid.GetCellValue(row, col)#在这里反序列化，传递给canvas
self.m_canvas.SetScales(pickle.loads(str(self.startValue)))

这样就可以摆脱GetCellValue只能返回wxString的限制了。把对象传输过来，用glCanvas来绘制。