def sed(patt_s, repl_s, filename1, filename2):
	try:
		fin = open(filename1, 'r')
		fout = open(filename2, 'w')
	except:
		print('file cannot be opened or created')
 
	for line in fin:
		if patt_s in line:
			fout.write(line.replace(patt_s, repl_s))
		else:
			fout.write(line)
 
	try:
		fout.close()
		fin.close()
	except:
		print('Files cannot be closed')
 
 
if __name__ == '__main__':
	sed('Alice', 'BOOOOOOM!!!!', 'alice.txt', 'result.txt')

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