String to function with parameters

Question

I'm relatively new to Python, but I have a lot of experience in languages like C++ and Java. I am trying to parse a string to a function with parameters. This is what I got so far:

def DimLights(percent = 1.0):
    print 'Dimming lights to ' + "{:.2f}".format(percent * 100) + ' percent'

def TurnOffLights():
    print 'Turning off lights'

function_mappings = {'DimLights': DimLights,
                     'TurnOffLights': TurnOffLights}

def select_function():
    while True:
        try:
            return function_mappings[raw_input('Please input the function you want to use')]
        except:
            print 'Invalid function, try again.'

while True:
    function = select_function()
    function()

It's working as long as I don't use any parameters, but I can't think of a solution that would work with parameters. Is there any way I can accomplish this?

So you want to pass an argument into select_function() that would be in turn passed into the function you select? — APerson
– APerson, Commented Mar 24, 2015 at 15:58
unsolicited tip: please never leave an except: to catch all errors. You probably want KeyError and some select others here. But you probably don't want SyntaxError et al. — Brian Cain
– Brian Cain, Commented Mar 24, 2015 at 15:59
@APerson: But what if I have more than one argument? Brian Cain: Thanks, I'll do that — TheKrane
– TheKrane, Commented Mar 24, 2015 at 16:13

Ignacio Vazquez-Abrams · Accepted Answer · 2015-03-24 15:57:28Z

1

Use str.split() with its maxsplit argument to strip off just the actual command, and argparse to parse the arguments.

answered Mar 24, 2015 at 15:57

Ignacio Vazquez-Abrams

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5 Comments

TheKrane Over a year ago

I'm sorry I'm a total noob when it comes to Python. Where exactly would I use str.split()?

Ignacio Vazquez-Abrams Over a year ago

The input is a str, so you'd use it right on the input. inputline = raw_input(...); command, arguments = inputline.split(maxsplit=1)

TheKrane Over a year ago

I don't know why I don't get this. So my input is for example: DimLights(1.0) Now I want to get rid of the'(1.0)' with inputline..split(maxsplit=1), right? And how do I parse the arguments. I feel really dumb right now.

Ignacio Vazquez-Abrams Over a year ago

If you simplify the input to "DimLights 1.0" then you can use this. The parens are just noise unless you're either programming or doing math.

TheKrane Over a year ago

Hmm I'm using python 2.7 and it gives me an error: split() takes no keyword arguments Is maxsplit a 3.4 feature?

itzMEonTV · Accepted Answer · 2015-03-24 16:28:40Z

0

Try this , Not a complete answer.But You can use it:

def DimLights(percent = 1.0):
    print 'Dimming lights to ' + "{:.2f}".format(percent * 100) + ' percent'

def TurnOffLights():
    print 'Turning off lights'

function_mappings = {'DimLights': DimLights,
                     'TurnOffLights': TurnOffLights}

def select_function():
    while True:
        try:
            inp = raw_input('Please input the function you want to use:')
            inp = inp.split()
            return function_mappings[inp[0]], inp[1]
        except:
            print 'Invalid function, try again.'
            break

function, arg = select_function()
function(float(arg))
# while True:
#     function = select_function
#     function()

>>>Please input the function you want to use:DimLights 2.0
Dimming lights to 200.00 percent

Note

Put space between function and parameter. Also parameter is required.Otherwise Index error will occur

answered Mar 24, 2015 at 16:28

itzMEonTV

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1 Comment

TheKrane Over a year ago

Thank you so much! This helped a lot!

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