import codecs, re
f = codecs.open(u'kontra.txt', 'r', 'utf-8-sig')
arr = []
doms = []
for line in f:
    for word in line.split():
        arr.append(word)
f.close()

for i in range(len(words)):
    dom = re.findall(u'^(.)(dom)$', words[i])
   doms.append(dom)       
f1 = codecs.open(u'doms.txt', 'w', 'utf-8')
for i in dom:
    f2.write(i + u' ')
f1.close()

for i in range(len(doms)):
    doms[i] = re.sub(u'\\b(s|m|t|w)(o|u|e|a)(day)', u'___\\4', doms[i], flags=re.U)
    f2 = codecs.open(u'days.txt', 'w', 'utf-8')
for i in doms:
    f2.write(i + u'\r\n')
f2.close()

>>> import re
>>> 
>>> text = 'abcd abcd1dom abcd abcd2dom'
>>> 
>>> lst = re.findall(r'\S*dom\b', text)
>>> print(lst)
['abcd1dom', 'abcd2dom']
>>>

>>> import re
>>> 
>>> text = 'abcd sunday abcd monday abcd tuesday ' \
...        'abcd wednesday abcd thursday abcd friday ' \
...        'abcd saturday abcd'
>>> 
>>> lst = re.findall(r'\b[^aeiouy][aeiouy]\S*day\b', text)
>>> print(lst)
['sunday', 'monday', 'tuesday', 'wednesday', 'saturday']
>>> 
>>> rtext = re.sub(r'\b[^aeiouy][aeiouy]\S*day\b', r'...day', text)
>>> print(rtext)
abcd ...day abcd ...day abcd ...day abcd ...day abcd thursday abcd friday abcd ...day abcd
>>>