使用内置format函数

d = 12345678
print format(d, ',')

其他方法

正则split

import re
d = 12345678
rsd = str(d)[::-1]
','.join(x for x in re.split(r'(\d{3})', rsd) if x)[::-1]  # 子组拆分

divmod

d = 12345678
l = []
while True:
    first, second = divmod(d, 1000)
    l.insert(0, str(second))
    if first:
        d = first
        continue
    break
 print ','.join(l)

• https://www.cnblogs.com/linxiyue/p/4183230.html