Mapytex/random_expression.py

#!/usr/bin/env python
# encoding: utf-8

from random import randint
import re

class RdExpression(object):
    """A generator of random expression builder"""

    def __init__(self, form, conditions = []):
        """Initiate the generator

        :param form: the form of the expression (/!\ variables need to be in brackets {})
        :param conditions: condition on variables (/!\ variables need to be in brackets {})

        """
        self._form = form
        self._conditions = conditions
        self._letters = self.get_letters()
        self._gene_varia = {}
        self._gene_2replaced= {}

    def get_2replaced(self):
        """Get elements of self._form which will have to be replaced
        :returns: set for elements which have to be replaced

        """
        pattern = "\{(.*?)\}" #select inside {} non greedy way
        varia = re.findall(pattern, self._form)
        varia = set(varia)
        self._2replaced = varia

        return varia
        
    def get_letters(self):
        """Find letters in the form
        :returns: list of letters

        """
        v2replaced = self.get_2replaced()
        varia = set()

        pattern = "([a-zA-Z]+)"
        for v in v2replaced:
            lvar = set(re.findall(pattern, v))
            varia = varia | lvar

        return varia


    def __call__(self, val_min = -10, val_max = 10):
        """RdExpression once it is initiate act like a function which create random expressions.

        :param val_min: minimum value random generation
        :param val_max: maximum value random generation
        :returns: an random expression

        """
        self.gene_varia(val_min, val_max)

        while not(self.val_conditions()):
            self.gene_varia(val_min, val_max)

        return self._form.format(**self._gene_2replaced)

    def gene_varia(self, val_min = -10, val_max = 10):
        """RAndomly generates variables/letters

        """
        for l in self._letters:
            self._gene_varia[l] = randint(val_min, val_max)

        for e in self._2replaced:
            self._gene_2replaced[e] = eval(e, globals(), self._gene_varia)

    def val_conditions(self):
        """Tells whether or not conditions are validates
        :returns: boolean

        """
        if self._conditions != []:
            return eval(" and ".join(self._conditions).format(**self._gene_varia))
        else:
            return True

def desc_rdExp(rdExp):
    print("--------------------")
    print("form: ",rdExp._form)
    print("Conditions: ",rdExp._conditions)
    print("Letters: ", rdExp._letters)
    print("2replaced: ", rdExp._2replaced)
    print("Call : ", rdExp())
    print("Gene varia: ", rdExp._gene_varia)
    print("Gene 2replaced: ", rdExp._gene_2replaced)
    print('')


if __name__ == '__main__':
    form = "{a}x + 2*{b}"
    cond = ["{a} + {b} in [1, 2, 3, 4, 5]", "{a} not in [0,1]", "{b} not in [0,1]"]
    rdExp1 = RdExpression(form, cond)
    desc_rdExp(rdExp1)
    rdExp2 = RdExpression(form)
    desc_rdExp(rdExp2)
    form = "{a+a/10}x + {a} + 2*{b}"
    cond = ["{a} + {b} in [1, 2, 3, 4, 5]", "{a} not in [0,1]", "{b} not in [0,1]"]
    rdExp3 = RdExpression(form)
    desc_rdExp(rdExp3)





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