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preper.py
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preper.py
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import re
class Preper():
"""
Does preprocessing of text in Farsi (Persian) language
"""
#THIS IS WHERE YOU READ STOP WORDS LIST
with open('stopwords.txt' , 'r', encoding = 'utf-8') as f:
stopwords_text = f.read()
stopwords = stopwords_text.split()
def __init__(self,text):
self.text = text
def stem_word(self,word):
"""
Finds Farsi (Persian) words stem
"""
# It is assumed that the stem has at least three letters.
# Also, the biggest Persian suffix has four letters
if len(word)<=3:
remove_suffix = False
remained_letters = []
else:
remove_suffix = True
remained_letters = list(word[3:])
while remove_suffix:
sufflen = 0
suff_letters = ['','','','']
for i in range(min(4,len(remained_letters))):
suff_letters[3-i] = remained_letters[-i-1]
#Sufixes: بر، تر، گر، دار، بار، گیر
if suff_letters[-1] == 'ر':
if suff_letters[-2] in ['ب','گ','ت']:
sufflen = 2
elif suff_letters[-2] == 'ا':
if suff_letters[-3] in ['ب','د']:
sufflen = 3
elif suff_letters[-2] == 'ی':
if suff_letters[-3] == 'گ':
sufflen = 3
#Sufixes: haa, aasaa
elif suff_letters[-1] == 'ا':
if suff_letters[-2] == 'ه':
sufflen = 2
elif suff_letters[-2] == 'س':
if suff_letters[-3] == 'ا':
sufflen = 3
#Sufixes: eem, yim, m, am
elif suff_letters[-1] == 'م':
if suff_letters[-2] == 'ا':
sufflen = 2
elif suff_letters[-2] == 'ی':
if suff_letters[-3] in ['ا','ی']:
sufflen = 3
else:
sufflen = 2
else:
sufflen = 1
#Suffixes: t, st, eet, aat
elif suff_letters[-1] == 'ت':
if suff_letters[-2] in ['ا','ی','س']:
sufflen = 2
else:
sufflen = 1
#Suffixes: ee, yee, gee
elif suff_letters[-1] == 'ی':
if suff_letters[-2] in ['ا','ی']:
sufflen = 2
elif suff_letters[-2] == 'گ':
sufflen=2
#Persian exception: add letter "he" to main word
remained_letters = remained_letters[:-2] + ['ه'] + remained_letters[-2:]
else:
sufflen = 1
#Suffixes: sh, ash, yash
elif suff_letters[-1] == 'ش':
if suff_letters[-2] in ['ا','ی']:
sufflen = 2
else:
sufflen = 1
#Suffixes: n, aan, een, saan, gaan
elif suff_letters[-1] == 'ن':
if suff_letters[-2] == 'ی':
sufflen = 2
elif suff_letters[-2] == 'ا':
if suff_letters[-3] == 'س':
sufflen = 3
elif suff_letters[-3] == 'گ':
sufflen = 3
remained_letters = remained_letters[:-3] + ['ه'] + remained_letters[-3:]
else:
sufflen = 2
else:
sufflen = 1
#Suffixes: nad, eed, yand, eed, and, abad
elif suff_letters[-1] == 'د':
if suff_letters[-2] in ['ی','ن']:
if suff_letters[-3] in ['ا','ی']:
sufflen = 3
else:
sufflen = 2
elif suff_letters[-2] =='ا':
if suff_letters[-3] == 'ب':
if suff_letters[-4] == 'ا':
sufflen = 4
#Suffixes: k, naak
elif suff_letters[-1] == 'ک':
if suff_letters[-2] == 'ا':
if suff_letters[-3] == 'ن':
sufflen = 3
else:
sufflen = 1
#Suffixes: baareh, gaaneh, gaah
elif suff_letters[-1] == 'ه':
if suff_letters[-2] == 'ر':
if suff_letters[-3] == 'ا':
if suff_letters[-4] == 'ب':
sufflen = 4
elif suff_letters[-2] == 'ا':
if suff_letters[-3] == 'گ':
sufflen = 3
elif suff_letters[-2] == 'ن':
if suff_letters[-3] == 'ا':
if suff_letters[-4] == 'گ':
sufflen = 4
if sufflen != 0:
remained_letters = remained_letters[:-sufflen]
if len(remained_letters) == 0 or sufflen == 0:
remove_suffix = False
word = word[:3] + ''.join(remained_letters)
#Remove prefix
if len(word) <= 3:
remove_prefix = False
remained_letters = []
else:
remove_prefix = True
remained_letters = list(word[:-3])
while remove_prefix:
prelen = 0
pre_letters = ['','','']
for i in range(min(len(remained_letters),3)):
pre_letters[i] = remained_letters[i]
#prefixes: ba, bar, baa
if pre_letters[0] == 'ب':
if pre_letters[1] in ['ا','ر']:
prelen = 2
else:
prelen = 1
#prefixes: na, naa
if pre_letters[0] == 'ن':
if pre_letters[1] == 'ا':
prelen=2
else:
prelen = 1
#prefixes: pish
if pre_letters[0] == 'پ':
if pre_letters[1] == 'ی':
if pre_letters[2] == 'ش':
prelen = 3
#prefixes: ham
if pre_letters[0] == 'ه':
if pre_letters[1] == 'م':
prelen = 2
#prefixes: mee
if pre_letters[0] == 'م':
if pre_letters[1] == 'ی':
prelen = 2
if prelen != 0:
remained_letters = remained_letters[prelen:]
if len(remained_letters) == 0 or prelen == 0:
remove_prefix = False
word = ''.join(remained_letters) + word[-3:]
return word
def remove_noise(self):
"""
Removes digits, punctuations, and non-Arabic letters characters from the text
"""
self.text = re.sub('\W+',' ',self.text)
self.text = re.sub('[a-zA-Z0-9]', ' ', self.text)
words = self.text.split()
#remove stop words and stemming words
words = list(filter(lambda word: word not in Preper.stopwords, words))
return words
def normalise_letter(self):
"""
Normalises the text by mapping diffrent glyphs of same letter to one glyph (the most common glyph).
"""
#Normalises letter ا"
self.text = re.sub('[ﭑآأإٱٲٳٵﭐ]','ا',self.text)
#Normalising letter "ت"
self.text = re.sub('[ةٹٺټٽۃ]','ت',self.text)
#Normalises letter "ک"
self.text = re.sub('[ػؼكڪګڬڭڮ]','ک',self.text)
#Normalises letter "گ"
self.text = re.sub('[ڰڱڲڳڴ]','گ',self.text)
#Normalises letter "و"
self.text = re.sub('[ۇؤٶ]','و',self.text)
#Normalises letter "ه"
self.text = re.sub('[ھہەﻫ]','ه',self.text)
#Normalises letter "ی"
self.text = re.sub('[ىي]','ی',self.text)