Unable to call function assigned to a variable in python

Question

I have the following code in which the function is not being called and an error is being returned. Following is the code -

def deleteExistingBackupFiles(step):
    try:
        for setting in step.Setting:
            key = setting['key']
            value = setting['value']
            configTable.update({key: value})
            if os.path.isfile(value):
                os.remove(value)
            elif os.path.isdir(value):
                shutil.rmtree(value)
    except:
        report.update({"DeleteExistingBackup":"There was a problem while trying to delete old files."})

def main():
    scriptPath = os.path.dirname(os.path.abspath(os.path.realpath(__file__)))
    configFilePath = os.path.abspath(os.path.realpath(scriptPath + '\config.xml'))
    parsedXML = ET.parse(configFilePath)

    #try:
    for step in parsedXML.iter('Step'):
        for setting in step.iter('Setting'):
            print setting.attrib.get('key')
            print setting.attrib.get('value')
            configTable.update({setting.attrib.get('key'): setting.attrib.get('value')})

    for step in tqdm(parsedXML.iter('Step'), desc='Wordpress Backup Restoration : '):
        methodName = step.attrib.get('methodname')
        result = methodName
        result(step)

While trying to execute the last statement, I am getting the following error -

Traceback (most recent call last):
  File "C:\Program Files\JetBrains\PyCharm 2017.1.2\helpers\pydev\pydevd.py", line 1585, in <module>
    globals = debugger.run(setup['file'], None, None, is_module)
  File "C:\Program Files\JetBrains\PyCharm 2017.1.2\helpers\pydev\pydevd.py", line 1015, in run
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "C:/Users/Pranav/PycharmProjects/DevEnv/Blog.py", line 119, in <module>
    main()
  File "C:/Users/Pranav/PycharmProjects/DevEnv/Blog.py", line 106, in main
    result(step)
TypeError: 'str' object is not callable

The methodName contains DeleteExistingBackupFiles yet it is still not working. Any idea what is going wrong?

Although when I try to execute the following code, it works fine -

def sampleFunc(arg):
    print('you called sampleFunc({})'.format(arg))

result = (sampleFunc)

result("Hello World!")

Have a nice day!

The difference between result = sampleFunc and result = "sampleFunc" — khelwood
– khelwood, Commented Jun 7, 2017 at 7:34
You're just assigning the name of the function to result, you're not assigning the function. You can't call a string. — Barmar
– Barmar, Commented Jun 7, 2017 at 7:36
@khelwood - Any idea how can I fix it in the code? Asking because the value which comes from XML is a string :( — Pranav Jituri
– Pranav Jituri, Commented Jun 7, 2017 at 7:36
Maybe you could have a dict to look up functions by a string. — khelwood
– khelwood, Commented Jun 7, 2017 at 7:37

acdr · Accepted Answer · 2017-06-07 07:36:18Z

2

You cannot call result because result is the name of the function, rather than the function itself. You could try evaluating the string to get the function (e.g. function = eval(result), function(step)) but that's kind of dubious. Instead, consider making a dictionary mapping function names to functions.

answered Jun 7, 2017 at 7:36

acdr

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Comments

zaidfazil · Accepted Answer · 2017-06-07 07:47:19Z

Embed the function in to a class object,

class Foo(object):

    def function_name(self, args):
        pass

Now, you can access the function from a string like this,

foo = Foo()
func_name = "function_name"
func = getattr(foo, func_name, None):
if func:
    func(arg)

In your code, if you wrap the function in a class, (say Foo),

class Foo(object):

    def deleteExistingBackupFiles(self, step):
        try:
            for setting in step.Setting:
                key = setting['key']
                value = setting['value']
                configTable.update({key: value})
                if os.path.isfile(value):
                    os.remove(value)
                elif os.path.isdir(value):
                    shutil.rmtree(value)
        except:
            report.update({"DeleteExistingBackup":"There was a problem while trying to delete old files."})

Then you could access the function,

foo = Foo()
result = getattr(foo, methodName, None)
if result:
    result(step)

Pranav Jituri · Accepted Answer · 2017-06-07 09:00:14Z

0

Rather than using the above methods, I utilized a dictionary as stated by @khelwood.

Added the following code before Main()

commandDispatcher = {
    "deleteExistingBackupFiles" : deleteExistingBackupFiles,
    "overwriteTestSiteData" : overwriteTestSiteData,
    "downloadProdBackup" : downloadProdBackup,
    "importSQL" : importSQL,
    "changeWPOptions" : changeWPOptions,
    "executeWPCli" : executeWPCli
}

Source - https://softwareengineering.stackexchange.com/a/182095

answered Jun 7, 2017 at 9:00

Pranav Jituri

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