进行动态导入，该导入在Python中仍然是显式的

好吧，这有点复杂

假设我在一个包中有一个模块：

a_package
 |-- __init__.py
 |-- a_module.py

在

a_模块.py中

我声明

a_类

：

# file location: a_package/a_module.py
class A_Class():
    def say(self):
        print ("cheese")

我可以创建一个

A_类

的实例，并通过以下操作调用

say

方法：

from a_package.a_module import A_Class
my_object = A_Class()
my_object.say() # this will display 'cheese' as expected

但是，我希望采用更动态的方法（我计划有很多包和类，并且希望使代码更易于编写）。因此，我创建了一个名为

load\u class

def load_class(package_name, module_name, class_name)
    result = None
    try:
        exec('from ' + package_name + '.' + module_name + ' import ' + class_name)
        exec('result = '+class_name)
    except:
        raise ImportError('Unable to load the class')
    return result

# Now, I can conveniently do this:
A_Class = load_class('a_package', 'a_module', 'A_Class')
my_object = A_Class()
my_object.say()

# or even shorter:
load_class('a_package', 'a_module', 'A_Class')().say()

程序按预期工作，但IDE（我使用pydev）不理解我的代码，无法执行intellisense（自动完成代码）

如果我使用第一种方法，intellisense显然是有效的：

from a_package.a_module import A_Class
my_object = A_Class()
my_object. # when I press ".", there will be a popup to let me choose "say" method

但如果我使用第二种方法，intellisense无法为我完成：

load_class('a_package', 'a_module', 'A_Class')(). # when I press ".", nothing happened

我知道，这是在Python中进行动态导入的折衷。但是，我想知道是否有其他方法可以让我使用第二种方法（可能不使用

exec

），它仍然可以让通用IDE的intellisense（如Pydev）猜测类内的方法

编辑：我为什么需要这样做？ 假设我有这样一个目录结构

fruit
 |-- strawberry.py
 |-- orange.py

chocolate
 |-- cadbury.py
 |-- kitkat.py

need_dynamic.py

在

need_dynamic.py

中，我有以下脚本：

food_list = ['fruit', 'chocolate']
subfood_list = [['strawberry', 'orange'],['cadbury', 'kitkat']] 
# show food list and ask user to choose food
for i in xrange(len(food_list)):
    print i + " : " + food_list[i]
food_index = int(raw_input('chose one'))
# show subfood list and ask user to choose subfood 
for i in xrange(len(subfood_list[food_index])):
    print i + " : " + subfood_list[food_index][i]
subfood_index = int(raw_input('chose one'))
# init the class
my_class = load_class(food_list[food_index], subfood_list[food_index, subfood_index])
# the rest of the code

这只是为了简化，实际上，我计划通过获取目录自动填充

食物列表

和

子食物列表

假设您有一个数据分类框架，并希望让用户选择他们想要使用的方法。用户还应该能够通过简单地添加python包和模块来扩展框架

我希望这个例子是合理的

---

再次编辑接受的答案无法解决智能感知问题。但它展示了如何更好地编写代码。我认为这是IDE的问题，而不是python的问题。我将发布另一个问题。

您希望使用

\uuu导入\uu

内置：

def load_class(package, mod_name, cls_name):
    mod = __import__('.'.join((package, mod_name)))
    return getattr(mod, cls_name)

---

当然，如果您愿意，您可以将错误处理放回那里，老实说，我不确定您首先为什么要这样做。对于大多数事情来说，动态导入似乎是一种“代码味道”。在开始使用之前，请评估您是否确实需要它。

好的，这是您的解决方案：

:/tmp/dynamic_import:~ ls
chocolate   fruit       need_dynamic.py
:/tmp/dynamic_import:~

need_dynamic.py

fruit
  |-- strawberry.py
  |-- orange.py

chocolate
 |-- cadbury.py
 |-- kitkat.py

:/tmp/dynamic_import:~ cat orange.py
class Orange(object):
    def say(self):
        return "Say cheese from class: %s" % __name__
:/tmp/dynamic_import:~

#!/usr/bin/env python

import os
import sys
import inspect

def load_modules_from_path(path):
    """
    Import all modules from the given directory
    """
    # Check and fix the path
    if path[-1:] != '/':
        path += '/'

    # Get a list of files in the directory, if the directory exists
    if not os.path.exists(path):
         raise OSError("Directory does not exist: %s" % path)

    # Add path to the system path
    sys.path.append(path)
    # Load all the files in path
    for f in os.listdir(path):
        # Ignore anything that isn't a .py file
        if len(f) > 3 and f[-3:] == '.py':
            modname = f[:-3]
            # Import the module
            __import__(modname, globals(), locals(), ['*'])

def load_class_from_name(fqcn):

    # fqcn = fully qualified classname
    # Break apart fqcn to get module and classname

    paths = fqcn.split('.')
    modulename = '.'.join(paths[:-1])
    classname = paths[-1]

    # Import the module
    __import__(modulename, globals(), locals(), ['*'])

    # Get the class
    cls = getattr(sys.modules[modulename], classname)
    # Check cls
    if not inspect.isclass(cls):
        raise TypeError("%s is not a class" % fqcn)

    # Return class
    return cls

def main():

    food_list = ['fruit', 'chocolate']
    subfood_list = [['strawberry', 'orange'],['cadbury', 'kitkat']]

    # show food list for users to select.
    for i in xrange(len(food_list)):
        print '%d: %s' % (i, food_list[i])

    food_index = int(raw_input('Choose one: '))

    for i in xrange(len(subfood_list[food_index])):
        print '%d: %s' % (i, subfood_list[food_index][i])

    subfood_index = int(raw_input('Chose one: '))
    pkg = food_list[food_index]
    module = subfood_list[food_index][subfood_index]
    class_name = module.title()

    load_modules_from_path(pkg)
    new_class = load_class_from_name('%s.%s' % (module, class_name))

    # instantiation
    obj = new_class()
    print obj.say()

if __name__ == '__main__': main()

:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 0
0: strawberry
1: orange
Chose one: 0
Say cheese from class: strawberry
:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 1
0: cadbury
1: kitkat
Chose one: 0
Say cheese from class: cadbury
:/tmp/dynamic_import:~

要使用名称作为字符串导入模块，请执行以下操作： 从模块路径加载类： 目录结构：

:/tmp/dynamic_import:~ ls
chocolate   fruit       need_dynamic.py
:/tmp/dynamic_import:~

need_dynamic.py

fruit
  |-- strawberry.py
  |-- orange.py

chocolate
 |-- cadbury.py
 |-- kitkat.py

:/tmp/dynamic_import:~ cat orange.py
class Orange(object):
    def say(self):
        return "Say cheese from class: %s" % __name__
:/tmp/dynamic_import:~

#!/usr/bin/env python

import os
import sys
import inspect

def load_modules_from_path(path):
    """
    Import all modules from the given directory
    """
    # Check and fix the path
    if path[-1:] != '/':
        path += '/'

    # Get a list of files in the directory, if the directory exists
    if not os.path.exists(path):
         raise OSError("Directory does not exist: %s" % path)

    # Add path to the system path
    sys.path.append(path)
    # Load all the files in path
    for f in os.listdir(path):
        # Ignore anything that isn't a .py file
        if len(f) > 3 and f[-3:] == '.py':
            modname = f[:-3]
            # Import the module
            __import__(modname, globals(), locals(), ['*'])

def load_class_from_name(fqcn):

    # fqcn = fully qualified classname
    # Break apart fqcn to get module and classname

    paths = fqcn.split('.')
    modulename = '.'.join(paths[:-1])
    classname = paths[-1]

    # Import the module
    __import__(modulename, globals(), locals(), ['*'])

    # Get the class
    cls = getattr(sys.modules[modulename], classname)
    # Check cls
    if not inspect.isclass(cls):
        raise TypeError("%s is not a class" % fqcn)

    # Return class
    return cls

def main():

    food_list = ['fruit', 'chocolate']
    subfood_list = [['strawberry', 'orange'],['cadbury', 'kitkat']]

    # show food list for users to select.
    for i in xrange(len(food_list)):
        print '%d: %s' % (i, food_list[i])

    food_index = int(raw_input('Choose one: '))

    for i in xrange(len(subfood_list[food_index])):
        print '%d: %s' % (i, subfood_list[food_index][i])

    subfood_index = int(raw_input('Chose one: '))
    pkg = food_list[food_index]
    module = subfood_list[food_index][subfood_index]
    class_name = module.title()

    load_modules_from_path(pkg)
    new_class = load_class_from_name('%s.%s' % (module, class_name))

    # instantiation
    obj = new_class()
    print obj.say()

if __name__ == '__main__': main()

:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 0
0: strawberry
1: orange
Chose one: 0
Say cheese from class: strawberry
:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 1
0: cadbury
1: kitkat
Chose one: 0
Say cheese from class: cadbury
:/tmp/dynamic_import:~

这是fruit中的一个模块，我用大写字母为模块名命名类名：

:/tmp/dynamic_import:~ ls
chocolate   fruit       need_dynamic.py
:/tmp/dynamic_import:~

need_dynamic.py

fruit
  |-- strawberry.py
  |-- orange.py

chocolate
 |-- cadbury.py
 |-- kitkat.py

:/tmp/dynamic_import:~ cat orange.py
class Orange(object):
    def say(self):
        return "Say cheese from class: %s" % __name__
:/tmp/dynamic_import:~

#!/usr/bin/env python

import os
import sys
import inspect

def load_modules_from_path(path):
    """
    Import all modules from the given directory
    """
    # Check and fix the path
    if path[-1:] != '/':
        path += '/'

    # Get a list of files in the directory, if the directory exists
    if not os.path.exists(path):
         raise OSError("Directory does not exist: %s" % path)

    # Add path to the system path
    sys.path.append(path)
    # Load all the files in path
    for f in os.listdir(path):
        # Ignore anything that isn't a .py file
        if len(f) > 3 and f[-3:] == '.py':
            modname = f[:-3]
            # Import the module
            __import__(modname, globals(), locals(), ['*'])

def load_class_from_name(fqcn):

    # fqcn = fully qualified classname
    # Break apart fqcn to get module and classname

    paths = fqcn.split('.')
    modulename = '.'.join(paths[:-1])
    classname = paths[-1]

    # Import the module
    __import__(modulename, globals(), locals(), ['*'])

    # Get the class
    cls = getattr(sys.modules[modulename], classname)
    # Check cls
    if not inspect.isclass(cls):
        raise TypeError("%s is not a class" % fqcn)

    # Return class
    return cls

def main():

    food_list = ['fruit', 'chocolate']
    subfood_list = [['strawberry', 'orange'],['cadbury', 'kitkat']]

    # show food list for users to select.
    for i in xrange(len(food_list)):
        print '%d: %s' % (i, food_list[i])

    food_index = int(raw_input('Choose one: '))

    for i in xrange(len(subfood_list[food_index])):
        print '%d: %s' % (i, subfood_list[food_index][i])

    subfood_index = int(raw_input('Chose one: '))
    pkg = food_list[food_index]
    module = subfood_list[food_index][subfood_index]
    class_name = module.title()

    load_modules_from_path(pkg)
    new_class = load_class_from_name('%s.%s' % (module, class_name))

    # instantiation
    obj = new_class()
    print obj.say()

if __name__ == '__main__': main()

:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 0
0: strawberry
1: orange
Chose one: 0
Say cheese from class: strawberry
:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 1
0: cadbury
1: kitkat
Chose one: 0
Say cheese from class: cadbury
:/tmp/dynamic_import:~

这是您的主要脚本：

:/tmp/dynamic_import:~ ls
chocolate   fruit       need_dynamic.py
:/tmp/dynamic_import:~

need_dynamic.py

fruit
  |-- strawberry.py
  |-- orange.py

chocolate
 |-- cadbury.py
 |-- kitkat.py

:/tmp/dynamic_import:~ cat orange.py
class Orange(object):
    def say(self):
        return "Say cheese from class: %s" % __name__
:/tmp/dynamic_import:~

#!/usr/bin/env python

import os
import sys
import inspect

def load_modules_from_path(path):
    """
    Import all modules from the given directory
    """
    # Check and fix the path
    if path[-1:] != '/':
        path += '/'

    # Get a list of files in the directory, if the directory exists
    if not os.path.exists(path):
         raise OSError("Directory does not exist: %s" % path)

    # Add path to the system path
    sys.path.append(path)
    # Load all the files in path
    for f in os.listdir(path):
        # Ignore anything that isn't a .py file
        if len(f) > 3 and f[-3:] == '.py':
            modname = f[:-3]
            # Import the module
            __import__(modname, globals(), locals(), ['*'])

def load_class_from_name(fqcn):

    # fqcn = fully qualified classname
    # Break apart fqcn to get module and classname

    paths = fqcn.split('.')
    modulename = '.'.join(paths[:-1])
    classname = paths[-1]

    # Import the module
    __import__(modulename, globals(), locals(), ['*'])

    # Get the class
    cls = getattr(sys.modules[modulename], classname)
    # Check cls
    if not inspect.isclass(cls):
        raise TypeError("%s is not a class" % fqcn)

    # Return class
    return cls

def main():

    food_list = ['fruit', 'chocolate']
    subfood_list = [['strawberry', 'orange'],['cadbury', 'kitkat']]

    # show food list for users to select.
    for i in xrange(len(food_list)):
        print '%d: %s' % (i, food_list[i])

    food_index = int(raw_input('Choose one: '))

    for i in xrange(len(subfood_list[food_index])):
        print '%d: %s' % (i, subfood_list[food_index][i])

    subfood_index = int(raw_input('Chose one: '))
    pkg = food_list[food_index]
    module = subfood_list[food_index][subfood_index]
    class_name = module.title()

    load_modules_from_path(pkg)
    new_class = load_class_from_name('%s.%s' % (module, class_name))

    # instantiation
    obj = new_class()
    print obj.say()

if __name__ == '__main__': main()

:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 0
0: strawberry
1: orange
Chose one: 0
Say cheese from class: strawberry
:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 1
0: cadbury
1: kitkat
Chose one: 0
Say cheese from class: cadbury
:/tmp/dynamic_import:~

以下是输出：

:/tmp/dynamic_import:~ ls
chocolate   fruit       need_dynamic.py
:/tmp/dynamic_import:~

need_dynamic.py

fruit
  |-- strawberry.py
  |-- orange.py

chocolate
 |-- cadbury.py
 |-- kitkat.py

:/tmp/dynamic_import:~ cat orange.py
class Orange(object):
    def say(self):
        return "Say cheese from class: %s" % __name__
:/tmp/dynamic_import:~

#!/usr/bin/env python

import os
import sys
import inspect

def load_modules_from_path(path):
    """
    Import all modules from the given directory
    """
    # Check and fix the path
    if path[-1:] != '/':
        path += '/'

    # Get a list of files in the directory, if the directory exists
    if not os.path.exists(path):
         raise OSError("Directory does not exist: %s" % path)

    # Add path to the system path
    sys.path.append(path)
    # Load all the files in path
    for f in os.listdir(path):
        # Ignore anything that isn't a .py file
        if len(f) > 3 and f[-3:] == '.py':
            modname = f[:-3]
            # Import the module
            __import__(modname, globals(), locals(), ['*'])

def load_class_from_name(fqcn):

    # fqcn = fully qualified classname
    # Break apart fqcn to get module and classname

    paths = fqcn.split('.')
    modulename = '.'.join(paths[:-1])
    classname = paths[-1]

    # Import the module
    __import__(modulename, globals(), locals(), ['*'])

    # Get the class
    cls = getattr(sys.modules[modulename], classname)
    # Check cls
    if not inspect.isclass(cls):
        raise TypeError("%s is not a class" % fqcn)

    # Return class
    return cls

def main():

    food_list = ['fruit', 'chocolate']
    subfood_list = [['strawberry', 'orange'],['cadbury', 'kitkat']]

    # show food list for users to select.
    for i in xrange(len(food_list)):
        print '%d: %s' % (i, food_list[i])

    food_index = int(raw_input('Choose one: '))

    for i in xrange(len(subfood_list[food_index])):
        print '%d: %s' % (i, subfood_list[food_index][i])

    subfood_index = int(raw_input('Chose one: '))
    pkg = food_list[food_index]
    module = subfood_list[food_index][subfood_index]
    class_name = module.title()

    load_modules_from_path(pkg)
    new_class = load_class_from_name('%s.%s' % (module, class_name))

    # instantiation
    obj = new_class()
    print obj.say()

if __name__ == '__main__': main()

:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 0
0: strawberry
1: orange
Chose one: 0
Say cheese from class: strawberry
:/tmp/dynamic_import:~ python need_dynamic.py
0: fruit
1: chocolate
Choose one: 1
0: cadbury
1: kitkat
Chose one: 0
Say cheese from class: cadbury
:/tmp/dynamic_import:~

---

请让我知道这是否有效。

您的方法比从package.module import klass执行

更好吗？后者更具语义，不会让其他程序员对您的代码感到困惑。这也让我可以通过使用配置变量调用不同的方法和类。我不知道intellisense是否能嗅出这个。（这似乎不太可能）。但是，如果要动态导入，这是一种方法（使用
\uuuu import\uuuu
而不是
exec
）。是的，您的代码看起来更干净。我也不确定。我相信这就是为什么web2py不是智能感知友好型的。为了更好的理由，为什么我要这么做，我编辑了我的答案。ThxUnfortuly似乎
getattr
只对类有效，而对模块无效，而且
inspect.get\u members（）
似乎太多了。当您有一堆模块并且不想加载所有内容时，动态导入非常有用。好的，
cls=getattr（sys.modules[modulename]，classname）
执行这个技巧即使我有一个大的监控脚本，我也会根据硬件类型加载模块和类，所以我不需要每次都将一堆模块加载到主脚本中。