Im trying to import files on Flask app in base of url route. I started to coding python few days ago so i havent idea if i doing it well. I write this on :
#app.route('/<file>')
def call(file):
__import__('controller.'+file)
hello = Example('Hello world')
return hello.msg
And i have other file called example.py into a controller folder that contains this:
class Example:
def __init__(self, msg):
self.msg = msg
So i start from terminal the app and i try to enter to localhost:5000/example.
Im trying to show in screen Hello world but give me the next error:
NameError: global name 'Example' is not defined
Thanks for all!
__import__ returns the newly imported module; names from that module are not added to your globals, so you need to get the Example class as an attribute from the returned module:
module = __import__('controller.'+file)
hello = module.Example('Hello world')
__import__ is rather low-level, you probably want to use importlib.import_module() instead:
import importlib
module = importlib.import_module('controller.'+file)
hello = module.Example('Hello world')
If you need to dynamically get the classname too, use getattr():
class_name = 'Example'
hello_class = getattr(module, class_name)
hello = hello_class('Hello world')
The Werkzeug package (used by Flask) offers a helpful functions here: werkzeug.utils.import_string() imports an object dynamically:
from werkzeug.utils import import_string
object_name = 'controller.{}:Example'.format(file)
hello_class = import_string(object_name)
This encapsulates the above process.
You'll need to be extremely careful with accepting names from web requests and using those as module names. Please do sanitise the file argument and only allow alphanumerics to prevent relative imports from being used.
You could use the werkzeug.utils.find_modules() function to limit the possible values for file here:
from werkzeug.utils import find_modules, import_string
module_name = 'controller.{}'.format(file)
if module_name not in set(find_modules('controller')):
abort(404) # no such module in the controller package
hello_class = import_string(module_name + ':Example')
I think you might not add the directory to the file, add the following code into the previous python program
# Add another directory
import sys
sys.path.insert(0, '/your_directory')
from Example import Example
There are two ways for you to do imports in Python:
import example
e = example.Example('hello world')
or
from example import Example
e = Example('hello world')
Related
I am trying to modify a better_profanity library to include an additional argument to get_replacement_for_swear_word function. To do so I first import the necessary parts of the library and test its functionality before:
from better_profanity import profanity, Profanity
text = "Nice c0ck"
censored = profanity.censor(text)
print(censored)
Now I get the source code of the class method, modify it and execute it to __main___:
from inspect import getsource
new_hide_swear_words = getsource(profanity._hide_swear_words).replace(
'get_replacement_for_swear_word(censor_char)', 'get_replacement_for_swear_word(censor_char, cur_word)').replace(
'ALLOWED_CHARACTERS', 'self.ALLOWED_CHARACTERS'
)
# fixing the indent
new_hide_swear_words = '\n'.join(i[4:] for i in new_hide_swear_words.split('\n'))
exec(new_hide_swear_words)
Now I replace this function inside the class:
profanity._hide_swear_words = _hide_swear_words.__get__(profanity, Profanity)
Note that I swap ALLOWED_CHARACTERS for self.ALLOWED_CHARACTERS. This is because the author of the library has imported ALLOWED_CHARACTERS in the same file where the class is defined, so when I swap the function and try to run the first piece of code again, it sais that this variable is not defined. It just so happens that it is stored in self as well, but there is no such luck with several other imported modules. Any ideas how to tackle this?
Here is the class definition on github.
When you run exec(new_hide_swear_words), you define the function _hide_swear_words in your current module (that's why you can access it later with just _hide_swear_words).
That however means, that the function lives fully in your module, so when you call it indirectly with profanity.censor(some_text) it will run the function inside this module and look for all dependent global symbols in your module.
That's why it can't access the variable ALLOWED_CHARACTERS or the function any_next_words_form_swear_words. They are defined in the profanity module, but not in your module where you run the exec.
One way to solve this, would be to just import all symbols into your module.
from inspect import getsource
from better_profanity import Profanity, profanity
from better_profanity.constants import ALLOWED_CHARACTERS
from better_profanity.utils import *
new_hide_swear_words = getsource(profanity._hide_swear_words)
new_hide_swear_words = "\n".join(i[4:] for i in new_hide_swear_words.split("\n"))
exec(new_hide_swear_words)
profanity._hide_swear_words = _hide_swear_words.__get__(profanity, Profanity)
text = "Nice c0ck"
censored = profanity.censor(text)
print(censored)
Another way would be to execute the function in the profanity module itself (then all the symbols are already defined).
However that also has a little overhead. E.g. you have to import the module and pass it to the exec function, and afterwards you need to extract the function from the module (as it will be defined in that module).
from importlib import import_module
from inspect import getsource
from better_profanity import Profanity, profanity
new_hide_swear_words = getsource(profanity._hide_swear_words)
# fixing the indent
new_hide_swear_words = "\n".join(i[4:] for i in new_hide_swear_words.split("\n"))
profanity_module = import_module(Profanity.__module__)
exec(new_hide_swear_words, vars(profanity_module))
profanity._hide_swear_words = profanity_module._hide_swear_words.__get__(
profanity, Profanity
)
text = "Nice c0ck"
censored = profanity.censor(text)
print(censored)
profanity_module = import_module(Profanity.__module__) is the same thing as import better_profanity.better_profanity as profanity_module.
I'm writing a Python application that takes a command as an argument, for example:
$ python myapp.py command1
I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like:
myapp/
__init__.py
commands/
__init__.py
command1.py
command2.py
foo.py
bar.py
So I want the application to find the available command modules at runtime and execute the appropriate one.
Python defines an __import__() function, which takes a string for a module name:
__import__(name, globals=None, locals=None, fromlist=(), level=0)
The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name.
Source: https://docs.python.org/3/library/functions.html#__import__
So currently I have something like:
command = sys.argv[1]
try:
command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"])
except ImportError:
# Display error message
command_module.run()
This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code.
Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added.
See also: How do I import a module given the full path?
With Python older than 2.7/3.1, that's pretty much how you do it.
For newer versions, see importlib.import_module for Python 2 and Python 3.
Or using __import__ you can import a list of modules by doing this:
>>> moduleNames = ['sys', 'os', 're', 'unittest']
>>> moduleNames
['sys', 'os', 're', 'unittest']
>>> modules = map(__import__, moduleNames)
Ripped straight from Dive Into Python.
The recommended way for Python 2.7 and 3.1 and later is to use importlib module:
importlib.import_module(name, package=None)
Import a module. The name argument specifies what module to import in absolute or relative terms (e.g. either pkg.mod or ..mod). If the name is specified in relative terms, then the package argument must be set to the name of the package which is to act as the anchor for resolving the package name (e.g. import_module('..mod', 'pkg.subpkg') will import pkg.mod).
e.g.
my_module = importlib.import_module('os.path')
Note: imp is deprecated since Python 3.4 in favor of importlib
As mentioned the imp module provides you loading functions:
imp.load_source(name, path)
imp.load_compiled(name, path)
I've used these before to perform something similar.
In my case I defined a specific class with defined methods that were required.
Once I loaded the module I would check if the class was in the module, and then create an instance of that class, something like this:
import imp
import os
def load_from_file(filepath):
class_inst = None
expected_class = 'MyClass'
mod_name,file_ext = os.path.splitext(os.path.split(filepath)[-1])
if file_ext.lower() == '.py':
py_mod = imp.load_source(mod_name, filepath)
elif file_ext.lower() == '.pyc':
py_mod = imp.load_compiled(mod_name, filepath)
if hasattr(py_mod, expected_class):
class_inst = getattr(py_mod, expected_class)()
return class_inst
Using importlib
Importing a source file
Here is a slightly adapted example from the documentation:
import sys
import importlib.util
file_path = 'pluginX.py'
module_name = 'pluginX'
spec = importlib.util.spec_from_file_location(module_name, file_path)
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
# Verify contents of the module:
print(dir(module))
From here, module will be a module object representing the pluginX module (the same thing that would be assigned to pluginX by doing import pluginX). Thus, to call e.g. a hello function (with no parameters) defined in pluginX, use module.hello().
To get the effect "importing" functionality from the module instead, store it in the in-memory cache of loaded modules, and then do the corresponding from import:
sys.modules[module_name] = module
from pluginX import hello
hello()
Importing a package
To import a package instead, calling import_module is sufficient. Suppose there is a package folder pluginX in the current working directory; then just do
import importlib
pkg = importlib.import_module('pluginX')
# check if it's all there..
print(dir(pkg))
Use the imp module, or the more direct __import__() function.
You can use exec:
exec("import myapp.commands.%s" % command)
If you want it in your locals:
>>> mod = 'sys'
>>> locals()['my_module'] = __import__(mod)
>>> my_module.version
'2.6.6 (r266:84297, Aug 24 2010, 18:46:32) [MSC v.1500 32 bit (Intel)]'
same would work with globals()
Similar as #monkut 's solution but reusable and error tolerant described here http://stamat.wordpress.com/dynamic-module-import-in-python/:
import os
import imp
def importFromURI(uri, absl):
mod = None
if not absl:
uri = os.path.normpath(os.path.join(os.path.dirname(__file__), uri))
path, fname = os.path.split(uri)
mname, ext = os.path.splitext(fname)
if os.path.exists(os.path.join(path,mname)+'.pyc'):
try:
return imp.load_compiled(mname, uri)
except:
pass
if os.path.exists(os.path.join(path,mname)+'.py'):
try:
return imp.load_source(mname, uri)
except:
pass
return mod
The below piece worked for me:
>>>import imp;
>>>fp, pathname, description = imp.find_module("/home/test_module");
>>>test_module = imp.load_module("test_module", fp, pathname, description);
>>>print test_module.print_hello();
if you want to import in shell-script:
python -c '<above entire code in one line>'
The following worked for me:
import sys, glob
sys.path.append('/home/marc/python/importtest/modus')
fl = glob.glob('modus/*.py')
modulist = []
adapters=[]
for i in range(len(fl)):
fl[i] = fl[i].split('/')[1]
fl[i] = fl[i][0:(len(fl[i])-3)]
modulist.append(getattr(__import__(fl[i]),fl[i]))
adapters.append(modulist[i]())
It loads modules from the folder 'modus'. The modules have a single class with the same name as the module name. E.g. the file modus/modu1.py contains:
class modu1():
def __init__(self):
self.x=1
print self.x
The result is a list of dynamically loaded classes "adapters".
Suppose I have 2 modules - one has been obfuscated by PyArmor. The other imports the obfuscated module and uses it:
# obfuscated.py
def run_task(conn):
conn.send_msg("Here you go")
print(conn.some_val + 55)
return 0
# Non obfuscated (user) code
import importlib.util
class conn:
some_val = 5
def send_msg(msg):
print(msg)
def main():
# import obfuscated # This works...but I need to dynamically load it:
# This does not:
spec = importlib.util.spec_from_file_location("module.name", r'c:\Users\me\obfuscated.py')
obfuscated = importlib.util.module_from_spec(spec)
spec.loader.exec_module(swdl)
ret = obfuscated.run_task(conn)
print("from main: ", ret)
if __name__ == "__main__":
main()
If I import the obfuscated file using import it is fine. But I need to use importlib to dynamically import the obfuscated file. The importlib does not work - I get:
AttributeError: module 'module.name' has no attribute 'obfuscated'
The idea is that the user can write a script using the API available within obfuscated.py but need to load the module from wherever it resides on their system.
Is there anyway to achieve this?
I think I have a method based on what I read here: https://pyarmor.readthedocs.io/en/latest/mode.html#restrict-mode
I use a proxy between the user code and the obfuscated code.
User code may or may not be obfuscated
The obfuscated code is obviously obfuscated!
The proxy must not be obfuscated (for simplicity, I obfuscated everything then copied the original proxy.py over the obfuscated one)
So, now user code imports the proxy.py using importlib instead of the obfuscated.py.
And the proxy merely imports the obfuscated.py:
# proxy.py
import obfuscated
I managed to import modules dynamically in this way:
code = open('c:\Users\me\obfuscated.py','r').read()
spec = importlib.util.spec_from_loader(package_name,loader=None)
module = importlib.util.module_from_spec(spec)
module.__file__ = 'c:\Users\me\obfuscated.py'
globals_dict = {"__file__":module.__file__}
exec(code, globals_dict)
for item in [x for x in globals_dict["__builtins__"] if not x.startswith("_")]:
setattr(module,item,globals_dict["__builtins__"].get(item))
It reads code from a file, initiates a module, and eventually puts variables in a dictionary. You can find the module's functions in globals_dict["__builtins__"]
I am using jython with a third party application. The third party application has some builtin libraries foo. To do some (unit) testing we want to run some code outside of the application. Since foo is bound to the application we decided to write our own mock implementation.
However there is one issue, we implemented our mock class in python while their class is in java. Thus to use their code one would do import foo and foo is the mock class afterwards. However if we import the python module like this we get the module attached to the name, thus one has to write foo.foo to get to the class.
For convenience reason we would love to be able to write from ourlib.thirdparty import foo to bind foo to the foo-class. However we would like to avoid to import all the classes in ourlib.thirdparty directly, since the loading time for each file takes quite a while.
Is there any way to this in python? ( I did not get far with Import hooks I tried simply returning the class from load_module or overwriting what I write to sys.modules (I think both approaches are ugly, particularly the later))
edit:
ok: here is what the files in ourlib.thirdparty look like simplified(without magic):
foo.py:
try:
import foo
except ImportError:
class foo
....
Actually they look like this:
foo.py:
class foo
....
__init__.py in ourlib.thirdparty
import sys
import os.path
import imp
#TODO: 3.0 importlib.util abstract base classes could greatly simplify this code or make it prettier.
class Importer(object):
def __init__(self, path_entry):
if not path_entry.startswith(os.path.join(os.path.dirname(__file__), 'thirdparty')):
raise ImportError('Custom importer only for thirdparty objects')
self._importTuples = {}
def find_module(self, fullname):
module = fullname.rpartition('.')[2]
try:
if fullname not in self._importTuples:
fileObj, self._importTuples[fullname] = imp.find_module(module)
if isinstance(fileObj, file):
fileObj.close()
except:
print 'backup'
path = os.path.join(os.path.join(os.path.dirname(__file__), 'thirdparty'), module+'.py')
if not os.path.isfile(path):
return None
raise ImportError("Could not find dummy class for %s (%s)\n(searched:%s)" % (module, fullname, path))
self._importTuples[fullname] = path, ('.py', 'r', imp.PY_SOURCE)
return self
def load_module(self, fullname):
fp = None
python = False
print fullname
if self._importTuples[fullname][1][2] in (imp.PY_SOURCE, imp.PY_COMPILED, imp.PY_FROZEN):
fp = open( self._importTuples[fullname][0], self._importTuples[fullname][1][1])
python = True
try:
imp.load_module(fullname, fp, *self._importTuples[fullname])
finally:
if python:
module = fullname.rpartition('.')[2]
#setattr(sys.modules[fullname], module, getattr(sys.modules[fullname], module))
#sys.modules[fullname] = getattr(sys.modules[fullname], module)
if isinstance(fp, file):
fp.close()
return getattr(sys.modules[fullname], module)
sys.path_hooks.append(Importer)
As others have remarked, it is such a plain thing in Python that the import statement iself has a syntax for that:
from foo import foo as original_foo, for example -
or even import foo as module_foo
Interesting to note is that the import statemente binds a name to the imported module or object ont he local context - however, the dictionary sys.modules (on the moduels sys of course), is a live reference to all imported modules, using their names as a key. This mechanism plays a key role in avoding that Python re-reads and re-executes and already imported module , when running (that is, if various of yoru modules or sub-modules import the samefoo` module, it is just read once -- the subsequent imports use the reference stored in sys.modules).
And -- besides the "import...as" syntax, modules in Python are just another object: you can assign any other name to them in run time.
So, the following code would also work perfectly for you:
import foo
original_foo = foo
class foo(Mock):
...
I have a string, say: abc.def.ghi.jkl.myfile.mymethod. How do I dynamically import mymethod?
Here is how I went about it:
def get_method_from_file(full_path):
if len(full_path) == 1:
return map(__import__,[full_path[0]])[0]
return getattr(get_method_from_file(full_path[:-1]),full_path[-1])
if __name__=='__main__':
print get_method_from_file('abc.def.ghi.jkl.myfile.mymethod'.split('.'))
I am wondering if the importing individual modules is required at all.
Edit: I am using Python version 2.6.5.
From Python 2.7 you can use the importlib.import_module() function. You can import a module and access an object defined within it with the following code:
from importlib import import_module
p, m = name.rsplit('.', 1)
mod = import_module(p)
met = getattr(mod, m)
met()
You don't need to import the individual modules. It is enough to import the module you want to import a name from and provide the fromlist argument:
def import_from(module, name):
module = __import__(module, fromlist=[name])
return getattr(module, name)
For your example abc.def.ghi.jkl.myfile.mymethod, call this function as
import_from("abc.def.ghi.jkl.myfile", "mymethod")
(Note that module-level functions are called functions in Python, not methods.)
For such a simple task, there is no advantage in using the importlib module.
For Python < 2.7 the builtin method __ import__ can be used:
__import__('abc.def.ghi.jkl.myfile.mymethod', fromlist=[''])
For Python >= 2.7 or 3.1 the convenient method importlib.import_module has been added. Just import your module like this:
importlib.import_module('abc.def.ghi.jkl.myfile.mymethod')
Update: Updated version according to comments (I must admit I didn't read the string to be imported till the end and I missed the fact that a method of a module should be imported and not a module itself):
Python < 2.7 :
mymethod = getattr(__import__("abc.def.ghi.jkl.myfile", fromlist=["mymethod"]))
Python >= 2.7:
mymethod = getattr(importlib.import_module("abc.def.ghi.jkl.myfile"), "mymethod")
from importlib import import_module
name = "file.py".strip('.py')
# if Path like : "path/python/file.py"
# use name.replaces("/",".")
imp = import_module(name)
# get Class From File.py
model = getattr(imp, "classNameImportFromFile")
NClass = model() # Class From file
It's unclear what you are trying to do to your local namespace. I assume you want just my_method as a local, typing output = my_method()?
# This is equivalent to "from a.b.myfile import my_method"
the_module = importlib.import_module("a.b.myfile")
same_module = __import__("a.b.myfile")
# import_module() and __input__() only return modules
my_method = getattr(the_module, "my_method")
# or, more concisely,
my_method = getattr(__import__("a.b.myfile"), "my_method")
output = my_method()
While you only add my_method to the local namespace, you do load the chain of modules. You can look at changes by watching the keys of sys.modules before and after the import. I hope this is clearer and more accurate than your other answers.
For completeness, this is how you add the whole chain.
# This is equivalent to "import a.b.myfile"
a = __import__("a.b.myfile")
also_a = importlib.import_module("a.b.myfile")
output = a.b.myfile.my_method()
# This is equivalent to "from a.b import myfile"
myfile = __import__("a.b.myfile", fromlist="a.b")
also_myfile = importlib.import_module("a.b.myfile", "a.b")
output = myfile.my_method()
And, finally, if you are using __import__() and have modified you search path after the program started, you may need to use __import__(normal args, globals=globals(), locals=locals()). The why is a complex discussion.
This website has a nice solution: load_class. I use it like this:
foo = load_class(package.subpackage.FooClass)()
type(foo) # returns FooClass
As requested, here is the code from the web link:
import importlib
def load_class(full_class_string):
"""
dynamically load a class from a string
"""
class_data = full_class_string.split(".")
module_path = ".".join(class_data[:-1])
class_str = class_data[-1]
module = importlib.import_module(module_path)
# Finally, we retrieve the Class
return getattr(module, class_str)
Use importlib (2.7+ only).
The way I tend to to this (as well as a number of other libraries, such as pylons and paste, if my memory serves me correctly) is to separate the module name from the function/attribute name by using a ':' between them. See the following example:
'abc.def.ghi.jkl.myfile:mymethod'
This makes the import_from(path) function below a little easier to use.
def import_from(path):
"""
Import an attribute, function or class from a module.
:attr path: A path descriptor in the form of 'pkg.module.submodule:attribute'
:type path: str
"""
path_parts = path.split(':')
if len(path_parts) < 2:
raise ImportError("path must be in the form of pkg.module.submodule:attribute")
module = __import__(path_parts[0], fromlist=path_parts[1])
return getattr(module, path_parts[1])
if __name__=='__main__':
func = import_from('a.b.c.d.myfile:mymethod')
func()
How about this :
def import_module(name):
mod = __import__(name)
for s in name.split('.')[1:]:
mod = getattr(mod, s)
return mod