背景

anaconda虚拟环境+windows10+python3.6.10+tensorflow2.2.0

错误1：Failed to import pydot. You must install pydot and graphviz for pydotprint to work.

错误1错误出错点：

使用plot_model将模型导出文件时报错。

from tensorflow.keras.utils import plot_model
plot_model(model, to_file='model.png')

Failed to import pydot. You must install pydot and graphviz for pydotprint to work.

错误1原因：

找不到pydot、graphviz。

错误1解决：

（1）安装pydot（pydot_ng或者pydotplus）

pip install pydot
pip install pydot_ng
pip install pydotplus

注意：有的教程说不能安装pydot，需要安装pydot_ng，我个人觉得这是不正确的说法，至少不能解决我的问题。
这三个安装任意一个都可以，根据源码（envs\dlpy\Lib\site-packages\tensorflow\python\keras\utils\vis_utils.py文件）：

try:  
  print("aaaa")
  # pydot-ng is a fork of pydot that is better maintained.
  import pydot_ng as pydot
except ImportError:
  # pydotplus is an improved version of pydot
  try:
    import pydotplus as pydot
  except ImportError:
    # Fall back on pydot if necessary.
    try:
      import pydot
    except ImportError:
      pydot = None

可以看到这里会去依次尝试导入pydot_ng、pydotplus、pydot，所以下载哪个都是一样的。

(2)安装graphviz

• 官网地址，我这里下载的是graphviz-install-2.44.1-win64
• 下载完成后，点击exe文件进行安装。（注意安装路径）

• 安装成功后，添加环境变量。（上一步中的路径，我这里是C:\Program Files\Graphviz 2.44.1\bin）

  
  添加环境变量

（3）重新激活anaconda虚拟环境，测试graphviz是否可以使用。

dot -version

出现graphviz版本信息：

graphviz版本信息

错误2：GraphViz's executables not found

错误2出错点：

找不到GraphViz

GraphViz's executables not found

错误2原因：

根据源码，判定graphviz路径有问题。

def find_graphviz():
    """Locate Graphviz's executables in the system.

    Tries three methods:

    First: Windows Registry (Windows only)
    This requires Mark Hammond's pywin32 is installed.

    Secondly: Search the path
    It will look for 'dot', 'twopi' and 'neato' in all the directories
    specified in the PATH environment variable.

    Thirdly: Default install location (Windows only)
    It will look for 'dot', 'twopi' and 'neato' in the default install
    location under the "Program Files" directory.

    It will return a dictionary containing the program names as keys
    and their paths as values.

    If this fails, it returns None.
    """

    # Method 1 (Windows only)
    if os.sys.platform == 'win32':

        HKEY_LOCAL_MACHINE = 0x80000002
        KEY_QUERY_VALUE = 0x0001

        RegOpenKeyEx = None
        RegQueryValueEx = None
        RegCloseKey = None

        try:
            import win32api
            RegOpenKeyEx = win32api.RegOpenKeyEx
            RegQueryValueEx = win32api.RegQueryValueEx
            RegCloseKey = win32api.RegCloseKey

        except ImportError:
            # Print a messaged suggesting they install these?
            pass

        try:
            import ctypes

            def RegOpenKeyEx(key, subkey, opt, sam):
                result = ctypes.c_uint(0)
                ctypes.windll.advapi32.RegOpenKeyExA(key, subkey, opt, sam,
                                                     ctypes.byref(result))
                return result.value

            def RegQueryValueEx(hkey, valuename):
                data_type = ctypes.c_uint(0)
                data_len = ctypes.c_uint(1024)
                data = ctypes.create_string_buffer(1024)

                # this has a return value, which we should probably check
                ctypes.windll.advapi32.RegQueryValueExA(
                    hkey, valuename, 0, ctypes.byref(data_type),
                    data, ctypes.byref(data_len))

                return data.value

            RegCloseKey = ctypes.windll.advapi32.RegCloseKey

        except ImportError:
            # Print a messaged suggesting they install these?
            pass

        if RegOpenKeyEx is not None:
            # Get the GraphViz install path from the registry
            hkey = None
            potentialKeys = [
                "SOFTWARE\\ATT\\Graphviz",
                "SOFTWARE\\AT&T Research Labs\\Graphviz"]
            for potentialKey in potentialKeys:

                try:
                    hkey = RegOpenKeyEx(
                        HKEY_LOCAL_MACHINE,
                        potentialKey, 0, KEY_QUERY_VALUE)

                    if hkey is not None:
                        path = RegQueryValueEx(hkey, "InstallPath")
                        RegCloseKey(hkey)

                        # The regitry variable might exist, left by
                        # old installations but with no value, in those cases
                        # we keep searching...
                        if not path:
                            continue

                        # Now append the "bin" subdirectory:
                        path = os.path.join(path, "bin")
                        progs = __find_executables(path)
                        if progs is not None:
                            return progs

                except Exception:
                    pass
                else:
                    break

    # Method 2 (Linux, Windows etc)
    if 'PATH' in os.environ:
        for path in os.environ['PATH'].split(os.pathsep):
            progs = __find_executables(path)
            if progs is not None:
                return progs


    # Method 3 (Windows only)
    if os.sys.platform == 'win32':

        # Try and work out the equivalent of "C:\Program Files" on this
        # machine (might be on drive D:, or in a different language)
        if 'PROGRAMFILES' in os.environ:
            # Note, we could also use the win32api to get this
            # information, but win32api may not be installed.
            path = os.path.join(os.environ['PROGRAMFILES'], 'ATT',
                                'GraphViz', 'bin')
        else:
            # Just in case, try the default...
            path = r"C:\Program Files\att\Graphviz\bin"

        progs = __find_executables(path)

        if progs is not None:
            return progs

    for path in (
            '/usr/bin', '/usr/local/bin',
            '/opt/local/bin',
            '/opt/bin', '/sw/bin', '/usr/share',
            '/Applications/Graphviz.app/Contents/MacOS/'):

        progs = __find_executables(path)
        if progs is not None:
            return progs

    # Failed to find GraphViz
    return None

错误2解决方法：

在上面的方法中手动写入graphviz路径，我这里是C:\Program Files\Graphviz 2.44.1\bin

    path = r"C:\Program Files\Graphviz 2.44.1\bin"
    progs = __find_executables(path)
    if progs is not None:
        return progs

修改完后的该方法为：

def find_graphviz():
    """Locate Graphviz's executables in the system.

    Tries three methods:

    First: Windows Registry (Windows only)
    This requires Mark Hammond's pywin32 is installed.

    Secondly: Search the path
    It will look for 'dot', 'twopi' and 'neato' in all the directories
    specified in the PATH environment variable.

    Thirdly: Default install location (Windows only)
    It will look for 'dot', 'twopi' and 'neato' in the default install
    location under the "Program Files" directory.

    It will return a dictionary containing the program names as keys
    and their paths as values.

    If this fails, it returns None.
    """

    # Method 1 (Windows only)
    if os.sys.platform == 'win32':

        HKEY_LOCAL_MACHINE = 0x80000002
        KEY_QUERY_VALUE = 0x0001

        RegOpenKeyEx = None
        RegQueryValueEx = None
        RegCloseKey = None

        try:
            import win32api
            RegOpenKeyEx = win32api.RegOpenKeyEx
            RegQueryValueEx = win32api.RegQueryValueEx
            RegCloseKey = win32api.RegCloseKey

        except ImportError:
            # Print a messaged suggesting they install these?
            pass

        try:
            import ctypes

            def RegOpenKeyEx(key, subkey, opt, sam):
                result = ctypes.c_uint(0)
                ctypes.windll.advapi32.RegOpenKeyExA(key, subkey, opt, sam,
                                                     ctypes.byref(result))
                return result.value

            def RegQueryValueEx(hkey, valuename):
                data_type = ctypes.c_uint(0)
                data_len = ctypes.c_uint(1024)
                data = ctypes.create_string_buffer(1024)

                # this has a return value, which we should probably check
                ctypes.windll.advapi32.RegQueryValueExA(
                    hkey, valuename, 0, ctypes.byref(data_type),
                    data, ctypes.byref(data_len))

                return data.value

            RegCloseKey = ctypes.windll.advapi32.RegCloseKey

        except ImportError:
            # Print a messaged suggesting they install these?
            pass

        if RegOpenKeyEx is not None:
            # Get the GraphViz install path from the registry
            hkey = None
            potentialKeys = [
                "SOFTWARE\\ATT\\Graphviz",
                "SOFTWARE\\AT&T Research Labs\\Graphviz"]
            for potentialKey in potentialKeys:

                try:
                    hkey = RegOpenKeyEx(
                        HKEY_LOCAL_MACHINE,
                        potentialKey, 0, KEY_QUERY_VALUE)

                    if hkey is not None:
                        path = RegQueryValueEx(hkey, "InstallPath")
                        RegCloseKey(hkey)

                        # The regitry variable might exist, left by
                        # old installations but with no value, in those cases
                        # we keep searching...
                        if not path:
                            continue

                        # Now append the "bin" subdirectory:
                        path = os.path.join(path, "bin")
                        progs = __find_executables(path)
                        if progs is not None:
                            return progs

                except Exception:
                    pass
                else:
                    break

    # Method 2 (Linux, Windows etc)
    if 'PATH' in os.environ:
        for path in os.environ['PATH'].split(os.pathsep):
            progs = __find_executables(path)
            if progs is not None:
                return progs

    path = r"C:\Program Files\Graphviz 2.44.1\bin"
    progs = __find_executables(path)
    if progs is not None:
        return progs

    # Method 3 (Windows only)
    if os.sys.platform == 'win32':

        # Try and work out the equivalent of "C:\Program Files" on this
        # machine (might be on drive D:, or in a different language)
        if 'PROGRAMFILES' in os.environ:
            # Note, we could also use the win32api to get this
            # information, but win32api may not be installed.
            path = os.path.join(os.environ['PROGRAMFILES'], 'ATT',
                                'GraphViz', 'bin')
        else:
            # Just in case, try the default...
            path = r"C:\Program Files\att\Graphviz\bin"

        progs = __find_executables(path)

        if progs is not None:
            return progs

    for path in (
            '/usr/bin', '/usr/local/bin',
            '/opt/local/bin',
            '/opt/bin', '/sw/bin', '/usr/share',
            '/Applications/Graphviz.app/Contents/MacOS/'):

        progs = __find_executables(path)
        if progs is not None:
            return progs

    # Failed to find GraphViz
    return None

错误3：pydot_ng.InvocationException:Program terminated with status:1. stderr follows: Format:“ps” not

错误3原因：

错误3原因

错误3解决方法：

dot -c

结果

重新运行代码，可以正常使用。

正常使用

参考