基本程序无法编译答案

【问题标题】：Basic program wont compile基本程序无法编译
【发布时间】：2015-04-21 13:27:28
【问题描述】：

我在 Windows 7 上使用 pycharm (python) (和 mapnik)，我只是想测试安装后是否一切就绪。我在这里使用了网上的一个例子，我有一个框架错误。会不会是安装问题？编译器？？我对python很陌生。提前感谢您的宝贵时间。

"""
This is a simple wxPython application demonstrates how to
integrate mapnik, it do nothing but draw the map from the World Poplulation XML
example:
https://github.com/mapnik/mapnik/wiki/GettingStartedInXML

Victor Lin. (bornstub@gmail.com)
Blog http://blog.ez2learn.com

"""

import mapnik
import wx


class Frame(wx.Frame):
        def __init__(self, *args, **kwargs):
            wx.Frame.__init__(self, size=(800, 500) ,*args, **kwargs)
            self.Bind(wx.EVT_PAINT, self.onPaint)

            self.mapfile = "population.xml"
            self.width = 800
            self.height = 500
            self.createMap()
            self.drawBmp()

        def createMap(self):
            """Create mapnik object

            """
            self.map = mapnik.Map(self.width, self.height)
            mapnik.load_map(self.map, self.mapfile)
            bbox = mapnik.Envelope(mapnik.Coord(-180.0, -75.0), mapnik.Coord(180.0, 90.0))
            self.map.zoom_to_box(bbox)

        def drawBmp(self):
            """Draw map to Bitmap object

            """
            # create a Image32 object
            image = mapnik.Image(self.width, self.height)
            # render map to Image32 object
            mapnik.render(self.map, image)
            # load raw data from Image32 to bitmap
            self.bmp = wx.BitmapFromBufferRGBA(self.width, self.height, image.tostring())

        def onPaint(self, event):
            dc = wx.PaintDC(self)
            memoryDC = wx.MemoryDC(self.bmp)
            # draw map to dc
            dc.Blit(0, 0, self.width, self.height, memoryDC, 0, 0)

        if __name__ == '__main__':

            app = wx.App()
        frame = frame(None, title="wxPython Mapnik Demo")
        frame.Show()
        app.MainLoop()

这里是错误信息：

 Traceback (most recent call last):
  File "C:/Python27/example.py", line 16, in <module>
    class Frame(wx.Frame):
  File "C:/Python27/example.py", line 56, in Frame
    frame = frame(None, title="wxPython Mapnik Demo")
NameError: name 'frame' is not defined

Process finished with exit code 1

【问题讨论】：

您正在调用一个名为 frame 的函数。 frame 未定义。你期待它吗？（也许你的意思是Frame？）Python 是一种区分大小写的语言，就像大多数语言一样。
哪个框架？节目里有很多
您创建了一个名为Frame 的类，它是wx.Frame 的子类。然后你尝试实例化它，但你拼错了。

标签： python wxpython pycharm mapnik

【解决方案1】：

您的代码存在一些问题。此行不正确：

frame = frame(None, title="wxPython Mapnik Demo")

应该是：

frame = Frame(None, title="wxPython Mapnik Demo")

原因是类名是Frame（不是大写F）并且你想实例化那个类来运行程序。另请注意，if __name__ == '__main__': 行的缩进不正确。以下完整示例应该可以工作：

import mapnik
import wx


class Frame(wx.Frame):
    def __init__(self, *args, **kwargs):
        wx.Frame.__init__(self, size=(800, 500) ,*args, **kwargs)
        self.Bind(wx.EVT_PAINT, self.onPaint)

        self.mapfile = "population.xml"
        self.width = 800
        self.height = 500
        self.createMap()
        self.drawBmp()

    def createMap(self):
        """Create mapnik object

        """
        self.map = mapnik.Map(self.width, self.height)
        mapnik.load_map(self.map, self.mapfile)
        bbox = mapnik.Envelope(mapnik.Coord(-180.0, -75.0), mapnik.Coord(180.0, 90.0))
        self.map.zoom_to_box(bbox)

    def drawBmp(self):
        """Draw map to Bitmap object

        """
        # create a Image32 object
        image = mapnik.Image(self.width, self.height)
        # render map to Image32 object
        mapnik.render(self.map, image)
        # load raw data from Image32 to bitmap
        self.bmp = wx.BitmapFromBufferRGBA(self.width, self.height, image.tostring())

    def onPaint(self, event):
        dc = wx.PaintDC(self)
        memoryDC = wx.MemoryDC(self.bmp)
        # draw map to dc
        dc.Blit(0, 0, self.width, self.height, memoryDC, 0, 0)

if __name__ == '__main__':

    app = wx.App()
    frame = Frame(None, title="wxPython Mapnik Demo")WAS WRONG
    frame.Show()
    app.MainLoop()

【讨论】：

【解决方案2】：

我认为 g 越来越好，我得到一个不同的错误：

    C:\Python27\python.exe C:/Python27/text.py
Traceback (most recent call last):
  File "C:/Python27/text.py", line 45, in <module>
    frame = Frame(None, title="wxPython Mapnik Demo")
  File "C:/Python27/text.py", line 13, in __init__
    self.createMap()
  File "C:/Python27/text.py", line 21, in createMap
    mapnik.load_map(self.map, self.mapfile)
RuntimeError: Could not load map file: File does not exist       of 'population.xml'

现在的 population.xml 文件是什么？？

【讨论】：