+ ：

1 s1 = 'a'2 s2 = 'b'3 s3 = 'c'4 s = 'I have ' + s1 +', ' + s2 + ', ' + s3 5 输出： 'I have a, b, c'

%：

1 s1 = 'a'2 s2 = 'b'3 s3 = 'c'4 s = 'I have %s, %s, %s'%(s1, s2, s3) 5 输出： 'I have a, b, c'

.format：

1 s1 = 'a'2 s2 = 'b'3 s3 = 'c'4 s = 'I have {}, {}, {}'.format(s1, s2, s3)5 输出： 'I have a, b, c'

推荐使用 .format 和 %方式拼接字符串。