content = '''email:12345678@163.com
email:2345678@163.com
email:345678@163.com
''' 

result_finditer = re.finditer(r"\d+@\w+.com", content)
#由于返回的为MatchObject的iterator，所以我们需要迭代并通过MatchObject的方法输出
for i in result_finditer :
  print i.group()

result_findall = re.findall(r"\d+@\w+.com", content)
#返回一个[] 直接输出or或者循环输出
print result_findall
for i in result_findall :
  print i 

result_finditer = re.finditer(r"(\d+)@(\w+).com", content)
#正则有两个分组，我们需要分别获取分区，分组从0开始，group方法不传递索引默认为0，代表了整个正则的匹配结果
for i in result_finditer :
  phone_no = i.group(1)
  email_type = i.group(2)

result_findall = re.findall(r"(\d+)@(\w+).com", content)
#此时返回的虽然为[]，但不是简单的[],而是一个tuple类型的list 
#如：[('12345678', '163'), ('2345678', '163'), ('345678', '163')]
for i in result_findall :
  phone_no = i[0]
  email_type = i[1] 

re.findall(r"\d+@\w+.com", content)
['2345678@163.com', '2345678@163.com', '345678@163.com'] 

re.findall(r"(\d+)@\w+.com", content)
['2345678', '2345678', '345678'] 

re.findall(r"(\d+)@(\w+).com", content)
[('2345678', '163'), ('2345678', '163'), ('345678', '163')] 

re.findall(r"((\d+)@(\w+).com)", content)
[('2345678@163.com', '2345678', '163'), ('2345678@163.com', '2345678', '163'), ('345678@163.com', '345678', '163')]