python source code of stemming

import nltk
from nltk.stem.lancaster import LancasterStemmer
from nltk.stem.porter import PorterStemmer
from nltk.stem.snowball import EnglishStemmer
from nltk.stem import WordNetLemmatizer
from flask import abort
from helpers import ret_success
from helpers import ret_failure
from helpers import parse_input
from helpers import penn_to_wn



LancasterSt = LancasterStemmer()
PorterSt = PorterStemmer()
SnowballSt = EnglishStemmer()
WordnetLm = WordNetLemmatizer()

def stemmer(method,data):
	"""
	Takes an array of words in JSON format.
	"""
	data = parse_input(data)
	if data == False:
		return ret_failure(703)
	else:
		res=[]
		if method == "lancaster":
			for word in data:
				try:
					res.append([word,LancasterSt.stem(word)])
				except:
					return ret_failure(702)
		elif method == "porter":
			for word in data:
				try:
					res.append([word,PorterSt.stem(word)])
				except:
					return ret_failure(702)
		elif method == 'snowball':
			for word in data:
				try:
					res.append([word,SnowballSt.stem(word)])
				except:
					return ret_failure(702)
		else:
			abort(404)
		return ret_success(res)

def lemmatize(method,data):
	"""
	Takes an array of words or array of tupples containing words and pos tags.
	Both Penn and Wordnet tags are supported
	"""
	data = parse_input(data)
	if data == False:
		return ret_failure(703)
	else:
		res=[]
		if method == "wordnet":
			for word in data:
				try:
					if type(word) is list:
						res.append([word[0],WordnetLm.lemmatize(word[0],penn_to_wn(word[1]))])
					else:	
						res.append([word,WordnetLm.lemmatize(word)])
				except LookupError: 
					return ret_failure(704)
				except:
					return ret_failure(702)
		else:
			abort(404)
		return ret_success(res)