Purpose

Randomregexp takes regular expressions and randomly generates strings maching them. It does not take any regular expression and there is a few things which can be added to the usual format, in particular to specify probability distributions.

Usage

import randregex.randregex as randregex
#Create the tree
tree = randregex.parse_rand_regex("toto|titi|tata")
#Generate a random regexp from the tree
res = randregex.produce_randregex_from_tree(mytree)

Format

• The pipe "exp1|exp2" : randomly generates "exp1" or "exp2" with probability 1/2 each.

  Example : "toto|tata|titi" generates "toto", "tata" or "titi" with probability 1/3 each.

• Groups "(exp)" : can be used to group things and change probabilities.

  Example : "My teacher (rocks|sucks)" generates "My teacher rocks" with probability 1/2 or "My teacher sucks" with probability 1/2.

  Example : "toto|(tata|titi)" generates "toto" with probability 1/2 and "tata" or "titi" with probability 1/4.

• Squared brackets "[a-z]" : can be used to randomly generate a character in the range.

  Example : "[abcxyz]" generates a character among {a, b, c, x, y, z} with probability 1/6 each.

  Example : "[a-z]" generates a character among {a, b, ..., z} with probability 1/26 each.

  Example : "[a-zA-Z0-9_]" generates a character among {a, ..., z, A, ..., Z, 0, ..., 9, _} with probability 1/63 each.

• Specify quantities - "{n,m}" : it is possible to specify a maximum and minimum number of time something is repeated.

  Example : "ahah{1,4}" generates "ahah", "ahahh", "ahahhh" or "ahahhhh" with probability 1/4 each.

  Example : "(ahah){1,4}" generates "ahah", "ahahahah", "ahahahahahah" or "ahahahahahahahah" with 1/4 probability each.

  Example : "(a|e|i){1,4}" generates between 1 and 4 letters picked among {a, e, i}.

  Example : "[0-9]{3}" generates three numbers.

  Example : "[0-9]{3,5}{97,99}{50}" generates between three and five numbers with 1/3 probability, between 97 and 99 numbers with 1/3 probability and 50 numbers with 1/3 probability.

• Random numbers - "%d" and "%f" : can be used to generate random integers or random floats. In this case quantities {n,m} means something different : the lower and upper bounds.

  Example : "%d{-543,543}" generates a random integer between -543 et 543.

  Example : "(%d{1,6} ){3}" generates three integer between 1 and 6 separated with a space.

  Example : "%f{-1.0,1.0}" generates a float between -1 and 1.

• The named groups "(?var=...)" and "($var)" : it is possible to name groups with ?= and reuse what was generated with $.

  Example : "(?var=%d{1,1000}) equals ($var)" generates a string of the form "n equals n" where n is randomly picked between 0 and 1000.

  Example : "(?blah=[a-z]{5}) is repeated twice in ($blah){2}" generates a string of the form "s is repeated twice in ss" where s is a string of 5 lowercase characters.

  Warning : "(?var=[a-z]{5}){2} is ($var) repeated twice" is not well defined because "[a-z]{5}" is repeated twice. The current format does not specify which of the two will be "($var)".

• Specify custom probabilities - "exp1<30>|exp2<70>" : It is possible to specify custom probabilities in three different ways : with pipes, inside squared brackets, and inside quantities. The specification of a probability of for instance 30% is done with "<30>".

  Example : "toto<10>|titi<20>|tata<70>" generates "toto" with 10% of chance, "titi" with 20% of chance and "tata" with 70% of chance.

  Example : "toto|titi|tata<97>" generates "toto" with 97% of chance, "titi" with 1.5% of chance and "tata" with 1.5% of chance.

  Example : "[a<30>e<50>iouy]" generates "a" with 30% of chance, "e" with 50% of chance, and "i", "o", "u" or "y" each with 5% of chance.

  Example : "[a-c<60>d-z_]" generates a letter among "a", "b" or "c" with 60% of chance, and a character among {d, ..., z, _} with probability (1/24) * 0.4.

  Example : "e{1,2<10>}{9,10}" generates with 10% of chance either "e" or "ee", and with 90% of chance either "eeeeeeeee" or "eeeeeeeeee".

  Warning : "toto<60>|tata<60>" gives an error because the sum of percentage goes above 100.

  Warning : "toto<60>|tata<10>" gives an error because the sum of percentage is below 100.

• Escaped characters : When we are not inside squared brackets, the following characters can be escaped (for other characters 'c', '\c' will be equal to '\c').

  • '\n' means end of line
  • '\t' means tabulation
  • '\(' means '('
  • '\)' means ')'
  • '\[' means '['
  • '\]' means ']'
  • '\|' means '|'
  • '\{' means '{'
  • '\}' means '}'
  • '\%' means '%'
  • '\<' means '<'
  • '\>' means '>'
  • '\\' means '\'

  When we are not inside square brackets, the following characters can be escaped :

  • '\[' means '['
  • '\]' means ']'
  • '\<' means '<'
  • '\>' means '>'
  • '\\' means '\'