Computing a function name from another function name

问题

In python 3.4, I want to be able to do a very simple dispatch table for testing purposes. The idea is to have a dictionary with the key being a string of the name of the function to be tested and the data item being the name of the test function.

For example:

myTestList = (
    "myDrawFromTo",
    "myDrawLineDir"
)

myTestDict = {
    "myDrawFromTo": test_myDrawFromTo,
    "myDrawLineDir": test_myDrawLineDir
}

for myTest in myTestList:
    result = myTestDict[myTest]()

The idea is that I have a list of function names someplace. In this example, I manually create a dictionary that maps those names to the names of test functions. The test function names are a simple extension of the function name. I'd like to compute the entire dictionary from the list of function names (here it is myTestList).

Alternately, if I can do the same thing without the dictionary, that'd be fine, too. I tried just building a new string from the entries in myTestList and then using local() to set up the call, but didn't have any luck. The dictionary idea came from the Python 3.x documentation.

回答1:

There are two parts to the problem.

The easy part is just prefixing 'text_' onto each string:

tests = {test: 'test_'+test for test in myTestDict}

The harder part is actually looking up the functions by name. That kind of thing is usually a bad idea, but you've hit on one of the cases (generating tests) where it often makes sense. You can do this by looking them up in your module's global dictionary, like this:

tests = {test: globals()['test_'+test] for test in myTestList}

There are variations on the same idea if the tests live somewhere other than the module's global scope. For example, it might be a good idea to make them all methods of a class, in which case you'd do:

tester = TestClass()
tests = {test: getattr(tester, 'test_'+test) for test in myTestList}

(Although more likely that code would be inside TestClass, so it would be using self rather than tester.)

If you don't actually need the dict, of course, you can change the comprehension to an explicit for statement:

for test in myTestList:
    globals()['test_'+test]()

One more thing: Before reinventing the wheel, have you looked at the testing frameworks built into the stdlib, or available on PyPI?

回答2:

Abarnert's answer seems to be useful but to answer your original question of how to call all test functions for a list of function names:

def test_f():
    print("testing f...")

def test_g():
    print("testing g...")

myTestList = ['f', 'g']

for funcname in myTestList:
    eval('test_' + funcname + '()')

来源：https://stackoverflow.com/questions/25799297/computing-a-function-name-from-another-function-name

标签

python

python-3.x

function

dispatch-table