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    <p>Yes, you can (for simple cases), but you need a bit of meta-programming. Like the other answers have said, a function does not declare that it throws a particular error type, so you need to look at the module and see what exception types it defines, or what exception types it raises. You can either try to grok the documentation or leverage the Python API to do this.</p> <p>To first find which exception types a module defines, just write a simple script to go through each object in the module dictionary <code>module.__dict__</code> and see if it ends in the word "Error" or if it is a subclass of Exception:</p> <pre><code>def listexns(mod): """Saved as: http://gist.github.com/402861 """ module = __import__(mod) exns = [] for name in module.__dict__: if (issubclass(module.__dict__[name], Exception) or name.endswith('Error')): exns.append(name) for name in exns: print '%s.%s is an exception type' % (str(mod), name) return </code></pre> <p>If I run this on your example of <code>shutils</code> I get this:</p> <pre><code>$ python listexn.py shutil Looking for exception types in module: shutil shutil.Error is an exception type shutil.WindowsError is an exception type $ </code></pre> <p>That tells you which error types are defined, but not which ones are thrown. To achieve the latter, we need to walk over the abstract syntax tree generated when the Python interpreter parses the module, and look for every <code>raise</code> statement, then save a list of names which are raised. The code for this is a little long, so first I'll state the output:</p> <pre><code>$ python listexn-raised.py /usr/lib/python2.6/shutil.py Looking for exception types in: /usr/lib/python2.6/shutil.py /usr/lib/python2.6/shutil.py:OSError is an exception type /usr/lib/python2.6/shutil.py:Error is an exception type $ </code></pre> <p>So, now we know that <code>shutil.py</code> defines the error types <code>Error</code> and <code>WindowsError</code> and raises the exception types <code>OSError</code> and <code>Error</code>. If we want to be a bit more complete, we could write another method to check every <code>except</code> clause to also see which exceptions <code>shutil</code> handles.</p> <p>Here's the code to walk over the AST, it just uses the <code>compiler.visitor</code> interface to create a walker which implements the "visitor pattern" from the Gang of Four book:</p> <pre><code>class ExceptionFinder(visitor.ASTVisitor): """List all exceptions raised by a module. Saved as: http://gist.github.com/402869 """ def __init__(self, filename): visitor.ASTVisitor.__init__(self) self.filename = filename self.exns = set() return def __visitName(self, node): """Should not be called by generic visit, otherwise every name will be reported as an exception type. """ self.exns.add(node.name) return def __visitCallFunc(self, node): """Should not be called by generic visit, otherwise every name will be reported as an exception type. """ self.__visitName(node.node) return def visitRaise(self, node): """Visit a raise statement. Cheat the default dispatcher. """ if issubclass(node.expr1, compiler.ast.Name): self.__visitName(node.expr1) elif isinstance(node.expr1, compiler.ast.CallFunc): self.__visitCallFunc(node.expr1) return </code></pre>
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    1. POHow Can I Find a List of All Exceptions That a Given Library Function Throws in Python?
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    1. CONo, you cannot list all exceptions, neither in theory nor practice: In practice, anything can raise many exceptions from the C part of python, from AssertionError to ZeroDivisionError. In theory, you can't find out what this raises: `raise type(raw_input("Raise What? "), (Exception,), {})` (it raises *a new type of exception* for every input)
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      1. USJochen Ritzel
    2. COOK, that's true, I'm only listing Python exceptions here and the static analysis won't catch your particular example. Your example shows that the question is uncomputable, but in practice a reasonable stab at an answer is probably all that is needed to use a piece of third-party code, which was what the OP was asking.
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    3. COI really appreciate this answer. I found it immensely useful and insightful. I didn't give you the answer credit, however, because after reading through the responses, it seems that there isn't really any foolproof way to find what I'm looking for. Your solution does seem to work in simple cases, but isn't convenient or elegant for common usage (would be a pain to run that for each function). But thank you for this anyway. It was very interesting.
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