def Open_Write_File_CharSet(FileName,CharSet):####
    return open(FileName,"w",CharSet)

def Write_In_File(File, Linea):####
    File.write(Linea)

def Close_Write_File( File):
    File.close

o = Open_Write_File_CharSet('demo.txt',1)
Write_In_File(o,'this is a new line')
Close_Write_File(o)

# Alternativa 1
o = open('demo.txt', 'w')
o.write('this is a new line')
o.close

# Alternativa 2
with open('demo2.txt','w') as o:
    o.write('this is a new line')