Function arguments in creating function file dynamically

Question

I'm trying to write a helper function to help me generate new file with function definition. Here are part of the code:

def new_function_file(file_name, fun_name, arguments):
  f = open(file_name + ".py", 'w')
  f.write("\tdef " + fun_name + str(("self", ) + arguments) + ":\n")

new_leetcode_file("testfile", "test", ("arr1", "arr2"))

However, this would generate "def test('self', 'arr1', 'arr2'):" in testfile.py. I was wondering how to properly parse the arguments without single quote generated?

What are you actually trying to achieve? Writing Python source code to a file from Python is only useful in rare circumstances. — Sven Marnach
– Sven Marnach, Commented Aug 9, 2015 at 20:03
Well... I want to write a helper function for online coding challenge, where I need to generate a template for unit-tests of the question along with the question description and the function definition. So I can save some time when doing the coding challenge for job interview. — Li-Fan Yu
– Li-Fan Yu, Commented Aug 9, 2015 at 20:39
I'd suggest to use some templating engine for this – you'll end up with much more readable code for the code generation. — Sven Marnach
– Sven Marnach, Commented Aug 9, 2015 at 21:04
The main issue is with str(("self", ) + arguments) + ":\n") If you get rid of the str( and closing ), you are creating a tuple with ("self", ) That means the expression ("self", ) + arguments will return a tuple. Then str gives you a string representation of that tuple, which is why you get the parentheses in your output. — bikemule
– bikemule, Commented Aug 9, 2015 at 21:09

isosceleswheel · Accepted Answer · 2015-08-09 20:28:15Z

3

Formatted printing might be useful here, along with breaking things down a bit:

def new_function_file(file_name, fun_name, arguments):

    f = open(file_name + ".py", 'w')

    # expand the arguments and join with "," separators:
    args = ", ".join(arguments) 
    # use formatted print to put it all together nicely:
    write_string = "\tdef {fn}(self, {ar}):\n".format(fn=fun_name, ar=args)

    f.write(write_string)

For your demo input:

new_leetcode_file("testfile", "test", ("arr1", "arr2"))

The "writestring" will be:

'\tdef test(self, arr1, arr2):\n'

and you can write this directly to the file without any other punctuation.

answered Aug 9, 2015 at 20:28

isosceleswheel

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1 Comment

bikemule Over a year ago

I voted this up rather than the third answer rather than @ForceBru because, while both correct, I think this is more pythonic and compact.

ForceBru · Accepted Answer · 2015-08-09 20:07:32Z

1

Here you're writing a tuple into your file while you have to write the contents of this tuple.

def new_function_file(file_name, fun_name, arguments):
   f = open(file_name + ".py", 'w')
   f.write("\tdef " + fun_name+"(")
   arguments=["self"].extend(list(arguments))
   for x in arguments:
      if x!=arguments[-1]: f.write(x+",")
      else: f.write(x)
   f.write("):\n")

answered Aug 9, 2015 at 20:07

ForceBru

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bikemule Over a year ago

I upvoted the other one because using join() is more compact/pythonic. join() is the first thing I thought of as well.

mgilson · Accepted Answer · 2015-08-09 20:10:42Z

1

You'd want '(' + ', '.join(('self',) + arguments) + ')' rather than str(('self',) + arguments).

With that said, there's probably a better way to accomplish whatever it is that you're trying to do ... I'll echo the comment by @SvenMarnach

"Writing Python source code to a file from Python is only useful in rare circumstances."

What are you actually trying to accomplish with this new python source file that you're generating?

edited Aug 9, 2015 at 20:10

answered Aug 9, 2015 at 20:07

mgilson

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2 Comments

ForceBru Over a year ago

Aren't you missing a ) after arguments?

mgilson Over a year ago

@ForceBru -- Thanks :-)

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