Extract arguments from string with python function

Question

I'm looking for a way to extract arguments embedded into python function returned to me as strings.

For example:

'create.copy("Node_A", "Information", False)'
# expected return: ["Node_A", "Information", "False"]

'create.new("Node_B")'
# expected return: ["Node_B"]

'delete("Node_C")'
# expected return: ["Node_C"]

My first approach was regular expressions like this:

re.match(r"("(.+?")")

But it returns None all the time.

How can I get list of this arguments?

BTW: I'm forced to use Python 2.7 and only built-in functions :(

All of your strings would be syntax errors. Please provide valid data and regex. — MisterMiyagi
– MisterMiyagi, Commented Sep 25, 2021 at 15:12

Leo · Accepted Answer · 2021-09-25 15:06:47Z

1

You can parse these expressions using the built-in ast module.

import ast

def get_args(expr):
    tree = ast.parse(expr)
    args = tree.body[0].value.args
    
    return [arg.value for arg in args]

get_args('create.copy("Node_A", "Information", False)') # ['Node_A', 'Information', False]
get_args('create.new("Node_B")') # ['Node_B']
get_args('delete("Node_C")') # ['Node_C']

answered Sep 25, 2021 at 15:06

Leo

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Comments

cards · Accepted Answer · 2021-09-25 23:19:53Z

0

Here an example without any external modules and totally compatible with python2.7. Slice the string w.r.t. the position of the brackets, clean it from extra white-spaces and split at ,.

f = 'create.copy("Node_A", "Information", False)'
i_open = f.find('(')
i_close = f.find(')')

print(f[i_open+1: i_close].replace(' ', '').split(','))

Output

['"Node_A"', '"Information"', 'False']

Remark:

not for nested functions.
the closing bracket can also be found by reversing the string

i_close = len(f) - f[::-1].find(')') - 1

edited Sep 25, 2021 at 23:19

answered Sep 25, 2021 at 15:10

cards

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Comments

balderman · Accepted Answer · 2021-09-25 15:08:57Z

0

See below (tested using python 3.6)

def get_args(expr):
    args = expr[expr.find('(') + 1:expr.find(')')].split(',')
    return [x.replace('"', '') for x in args]


entries = ['create.copy("Node_A", "Information", False)', "create.new(\"Node_B\")"]
for entry in entries:
    print(get_args(entry))

output

   ['Node_A', ' Information', ' False']
   ['Node_B']

answered Sep 25, 2021 at 15:08

balderman

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