>>> a = [(4,2,3), (5, 9, 1), (7,8,9)]

>>> from itertools import chain

>>> list(chain.from_iterable(a))

[4, 2, 3, 5, 9, 1, 7, 8, 9]

>>> from tkinter import _flatten   # python2.7也可以from compiler.ast import flatten

>>> _flatten(a)

(4, 2, 3, 5, 9, 1, 7, 8, 9)

>>> [','.join(map(str,t)) for t in a]

['4,2,3', '5,9,1', '7,8,9']

>>> from itertools import starmap

>>> list(starmap('{},{},{}'.format,a))

['4,2,3', '5,9,1', '7,8,9']

#笨办法，但是可以提供一种思路

a = [(4, 2, 3), (5,9,1), (7,8,9)]

i=0

while i<3:

    a[i]=str(a[i])[1:3*3-1]

    i=i+1

print (a[0:3])

>>>

['4, 2, 3', '5, 9, 1', '7, 8, 9']