So what I&#39;m looking for here is something like PHP&#39;s [print_r][1] function.

This is so I can debug my scripts by seeing what&#39;s the state of the object in question.


  [1]: http://us2.php.net/print_r

Is there a built-in function to print all the current properties and values of an object?

Given the Python function:

    def a_method(arg1, arg2):
        pass

How can I extract the number and names of the arguments. I.e., given that I have a reference to `func`, I want the `func.[something]` to return `(&quot;arg1&quot;, &quot;arg2&quot;)`.

The usage scenario for this is that I have a decorator, and I wish to use the method arguments in the same order that they appear for the actual function as a key. I.e., how would the decorator look that printed `&quot;a,b&quot;` when I call `a_method(&quot;a&quot;, &quot;b&quot;)`?


How to get method parameter names?

I&#39;d like to log the *call trace* during certain points, like failed assertions, or uncaught exceptions.


How do you print out a stack trace to the console/log in Cocoa?

How do I check if an object is an instance of a [Named tuple][1]?


  [1]: http://docs.python.org/dev/library/collections.html#namedtuple-factory-function-for-tuples-with-named-fields

How to check if an object is an instance of a namedtuple?

I&#39;m trying to pick up a bit of Swift lang and I&#39;m wondering how to convert the following Objective-C into Swift:

    - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
        [super touchesBegan:touches withEvent:event];

        UITouch *touch = [touches anyObject];

        if ([touch.view isKindOfClass: UIPickerView.class]) {
          //your touch was in a uipickerview ... do whatever you have to do
        }
    }

More specifically I need to know how to use `isKindOfClass` in the new syntax.

    override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {

        ???

        if ??? {
            // your touch was in a uipickerview ...
           
        }
    }

Using isKindOfClass with Swift

Python: How to get the caller&#39;s method name in the called method?

Assume I have 2 methods:

    def method1(self):
        ...
        a = A.method2()

    def method2(self):
        ...

If I don&#39;t want to do any change for method1, how to get the name of the caller (in this example, the name is method1) in method2?

How to get the caller&#39;s method name in the called method?

What does the `/` mean in Python 3.4&#39;s `help` output for `range` before the closing parenthesis?

    &gt;&gt;&gt; help(range)
    Help on class range in module builtins:
    
    class range(object)
     |  range(stop) -&gt; range object
     |  range(start, stop[, step]) -&gt; range object
     |  
     |  Return a virtual sequence of numbers from start to stop by step.
     |  
     |  Methods defined here:
     |  
     |  __contains__(self, key, /)
     |      Return key in self.
     |  
     |  __eq__(self, value, /)
     |      Return self==value.

                                            ...

What does the slash mean in help() output?

Given a class `Foo` (whether it is a [new-style][1] class or not), how do you generate **all** the base classes - anywhere in the inheritance hierarchy - it [`issubclass`][2] of?


  [1]: http://docs.python.org/reference/datamodel.html#new-style-and-classic-classes
  [2]: http://docs.python.org/library/functions.html?highlight=issubclass#issubclass

List all base classes in a hierarchy of given class?

Given a Django model, I&#39;m trying to list all of its fields.  I&#39;ve seen some examples of doing this using the _meta model attribute, but doesn&#39;t the underscore in front of meta indicate that the _meta attribute is a private attribute and shouldn&#39;t be accessed directly?  ... Because, for example, the layout of _meta could change in the future and not be a stable API?   

Is _meta an exception to this rule?  Is it stable and ready to use or is it considered bad practice to access it?  Or is there a function or some other way to introspect the fields of a model without using the _meta attribute?  Below is a list of some links showing how to do this using the _meta attribute

Any advice is much appreciated.  

&lt;a href=&quot;https://stackoverflow.com/questions/763558/django-object-get-set-field&quot;&gt;https://stackoverflow.com/questions/763558/django-object-get-set-field&lt;/a&gt;

&lt;a href=&quot;http://www.djangofoo.com/80/get-list-model-fields&quot;&gt;http://www.djangofoo.com/80/get-list-model-fields&lt;/a&gt;

https://stackoverflow.com/questions/2384436/how-to-introspect-django-model-fields

Get model&#39;s fields in Django

I&#39;ve a Java object &#39;ChildObj&#39; which is extended from &#39;ParentObj&#39;. Now, if it is possible to retrieve all the attribute names and values of ChildObj, including the inherited attributes too, using Java reflection mechanism?

[Class.getFields][1] gives me the array of public attributes, and [Class.getDeclaredFields][2] gives me the array of all fields, but none of them includes the inherited fields list.

Is there any way to retrieve the inherited attributes also?


  [1]: http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Class.html#getFields()
  [2]: http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Class.html#getDeclaredFields()

Retrieving the inherited attribute names/values using Java Reflection

In Python, without using the `traceback` module, is there a way to determine a function&#39;s name from within that function?

Say I have a module `foo` with a function `bar`.  When executing `foo.bar()`, is there a way for `bar` to know `bar`&#39;s name?  Or better yet, `foo.bar`&#39;s name?

    #foo.py  
    def bar():
        print &quot;my name is&quot;, __myname__ # &lt;== how do I calculate this at runtime?

Determine function name from within that function (without using traceback)

Say you have a javascript object like this:

    var data = { foo: &#39;bar&#39;, baz: &#39;quux&#39; };

You can access the properties by the property name:

    var foo = data.foo;
    var baz = data[&quot;baz&quot;];

But is it possible to get these values if you don&#39;t know the name of the properties? Does the unordered nature of these properties make it impossible to tell them apart?

In my case I&#39;m thinking specifically of a situation where a function needs to accept a series of name-value pairs, but the names of the properties may change.

My thoughts on how to do this so far is to pass the names of the properties to the function along with the data, but this feels like a hack. I would prefer to do this with introspection if possible.

How do I access properties of a javascript object if I don&#39;t know the names?

Given a Python object of any kind, is there an easy way to get the list of all methods that this object has?

Or,

if this is not possible, is there at least an easy way to check if it has a particular method other than simply checking if an error occurs when the method is called?

Finding what methods a Python object has

I am trying to dynamically create a `class` instance based type using generics, however I am encountering difficulty with class introspection.

Here are the questions:

 - Is there a Swift-equivalent to Obj-C&#39;s `self.class`?
 - Is there a way to instantiate a class using the `AnyClass` result from `NSClassFromString`?
 - Is there a way to get `AnyClass` or otherwise type information strictly from a generic parameter `T`? (Similar to C#&#39;s `typeof(T)` syntax)


Swift class introspection &amp; generics

Is there a straightforward way to find all the modules that are part of a python package? I&#39;ve found [this old discussion][1], which is not really conclusive, but I&#39;d love to have a definite answer before I roll out my own solution based on os.listdir().


  [1]: http://bytes.com/topic/python/answers/36924-how-get-list-modules-package

List all the modules that are part of a python package?

Given a class C in Python, how can I determine which file the class was defined in? I need something that can work from either the class C, or from an instance off C.

The reason I am doing this, is because I am generally a fan off putting files that belong together in the same folder. I want to create a class that uses a Django template to render itself as HTML. The base implementation should infer the filename for the template based on the filename that the class is defined in.

Say I put a class LocationArtifact in the file &quot;base/artifacts.py&quot;, then I want the default behaviour to be that the template name is &quot;base/LocationArtifact.html&quot;.

How do I get the filepath for a class in Python?

Suppose `myapp/foo.py` contains:

    def info(msg):
        caller_name = ????
        print &#39;[%s] %s&#39; % (caller_name, msg)

And `myapp/bar.py` contains:

    import foo
    foo.info(&#39;Hello&#39;) # =&gt; [myapp.bar] Hello

I want `caller_name` to be set to the `__name__` attribute of the calling functions&#39; module (which is &#39;myapp.foo&#39;) in this case. How can this be done?




Get __name__ of calling function&#39;s module in Python

I have a dict, which I need to pass key/values as keyword arguments.. For example..

    d_args = {&#39;kw1&#39;: &#39;value1&#39;, &#39;kw2&#39;: &#39;value2&#39;}
    example(**d_args)

This works fine, *but* if there are values in the d_args dict that are not accepted by the `example` function, it obviously dies.. Say, if the example function is defined as `def example(kw2):`

This is a problem since I don&#39;t control either the generation of the `d_args`, or the `example` function.. They both come from external modules, and `example` only accepts some of the keyword-arguments from the dict..

Ideally I would just do

    parsed_kwargs = feedparser.parse(the_url)
    valid_kwargs = get_valid_kwargs(parsed_kwargs, valid_for = PyRSS2Gen.RSS2)
    PyRSS2Gen.RSS2(**valid_kwargs)

I will probably just filter the dict, from a list of valid keyword-arguments, but I was wondering: **Is there a way to programatically list the keyword arguments the a specific function takes?**

Can you list the keyword arguments a function receives?

Say I have a variable named `choice` it is equal to 2. How would I access the name of the variable? Something equivalent to

    In [53]: namestr(choice)
    Out[53]: &#39;choice&#39;

for use in making a dictionary. There&#39;s a good way to do this and I&#39;m just missing it.

EDIT:

The reason to do this is thus. I am running some data analysis stuff where I call the program with multiple parameters that I would like to tweak, or not tweak, at runtime. I read in the parameters I used in the last run from a .config file formated as

    filename
    no_sig_resonance.dat
    
    mass_peak
    700
    
    choice
    1,2,3

When prompted for values, the previously used is displayed and an empty string input will use the previously used value.

My question comes about because when it comes to writing the dictionary that these values have been scanned into. If a parameter is needed I run `get_param` which accesses the file and finds the parameter. 

I think I will avoid the problem all together by reading the .`config` file once and producing a dictionary from that. I avoided that originally for... reasons I no longer remember. Perfect situation to update my code!

How can you print a variable name in python?

What is the difference? When should I use which? Why are there so many of them?

Ruby: kind_of? vs. instance_of? vs. is_a?

How can I get a list (in the form of an `NSArray` or `NSDictionary`) of a given object properties in Objective-C?  

Imagine the following scenario: I have defined a parent class which just extends `NSObject`, that holds an `NSString`, a `BOOL` and an `NSData` object as properties. Then I have several classes which extend this parent class, adding a lot of different properties each.  

Is there any way I could implement an instance method on the *parent* class that goes through the whole object and returns, say, an `NSArray` of each of the (child) class properties as `NSStrings` that are *not* on the parent class, so I can later use these `NSString` for KVC?

Get an object properties list in Objective-C

Is there a way to get **all** attributes/methods/fields/etc. of an object in Python?

`vars()` is *close* to what I want, but it doesn&#39;t work unless an object has a `__dict__`, which isn&#39;t always true (e.g. it&#39;s not true for a `list`, a `dict`, etc.).

Get all object attributes in Python?

I know you can do

    this.GetType().FullName

To get

    My.Current.Class

But what can I call to get

    My.Current.Class.CurrentMethod



How to get the name of the current method from code

I know of `is` and `as` for `instanceof`, but what about the reflective [isInstance()][1] method?

  [1]: http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Class.html#isInstance(java.lang.Object)


What is the C# equivalent to Java&#39;s isInstance()?

How do I find out a name of class that created an instance of an object in Python if the function I am doing this from is the base class of which the class of the instance has been derived?

Was thinking maybe [the inspect module][1] might have helped me out here, but it doesn&#39;t seem to give me what I want. And short of parsing the `__class__` member, I&#39;m not sure how to get at this information.


  [1]: https://docs.python.org/2/library/inspect.html &quot;inspect — Inspect live objects&quot;

Getting the class name of an instance?

I&#39;d like to get the name of the current `Activity` to be sent along in the URI of an `HttpRequest`. Is there a way to do this without referring specifically to the `Activity`?

I know I can do `myActivity.class.toString()` but this is just a less efficient way of hard coding &quot;myActivity&quot; since I&#39;m making a static reference to my `Activity`. Is there a more general way to do this using something like &#39;this&#39; (which btw doesn&#39;t actually work here because it returns more information than what&#39;s desired).

Get Activity name dynamically - android

In Java, you can do `instanceof`. Is there a Ruby equivalent? 

How do I check if a variable is an instance of a class?

Is there a built in method, function, API, commonly accepted way, etc. to dump the contents of an instantiated object in Objective-C, specifically in Apple&#39;s Cocoa/Cocoa-Touch environment?

I want to be able to do something like

	MyType *the_thing = [[MyType alloc] init];
	NSString *the_dump = [the_thing dump]; //pseudo code
	NSLog(&quot;Dumped Contents: %@&quot;, the_dump);
	
and have the object&#39;s instance variable names and values displayed, along with any methods available to call at run time. Ideally in an easy to read format.

For developers familiar with PHP, I&#39;m basically looking for the equivalent of the reflection functions (`var_dump()`, `get_class_methods()`) and the OO Reflection API. 


Objective-C Introspection/Reflection

    class C(object):
        def f(self):
            print self.__dict__
            print dir(self)
    c = C()
    c.f()

output:

    {}

    [&#39;__class__&#39;, &#39;__delattr__&#39;,&#39;f&#39;,....]

why there is not a &#39;f&#39; in self.\__dict__ 

What&#39;s the biggest difference between dir() and __dict__ in Python

Suppose `o` is a Python object, and I want all of the fields of `o`, without any methods or `__stuff__`. How can this be done?

I&#39;ve tried things like:

    [f for f in dir(o) if not callable(f)]

    [f for f in dir(o) if not inspect.ismethod(f)]

but these return the same as `dir(o)`, presumably because `dir` gives a list of strings. Also, things like `__class__` would be returned here, even if I get this to work.

How to list all fields of a class (and no methods)?

Can any one explain the use of Java reflection and introspection? When we need to use both?


Java introspection and reflection

I&#39;m starting to code in various projects using Python (including Django web development and Panda3D game development). 

To help me understand what&#39;s going on, I would like to basically &#39;look&#39; inside the Python objects to see how they tick - like their methods and properties. 

So say I have a Python object, what would I need to print out its contents? Is that even possible?



How do I look inside a Python object?

Can anyone explain from a language/environment agnostic perspective the difference between these two notions?

Also is there a set of conditions that programming languages need to satisfy in order to be reflective and/or introspective?

And if there is, what are these conditions?

All Introspection Solutions on Gang of Coders

Total of 33 Introspection Solutions