Python：将元组转换为逗号分隔的字符串

Question

import MySQLdb

db = MySQLdb.connect("localhost","root","password","database")
cursor = db.cursor()
cursor.execute("SELECT id FROM some_table")
u_data = cursor.fetchall()

>>> print u_data
((1320088L,),)

我在网上找到的东西让我到了这里：

string = ((1320088L,),)
string = ','.join(map(str, string))
>>> print string
(1320088L,)

我希望输出看起来像什么：

 #Single element expected result
 1320088L  
 #comma separated list if more than 2 elements, below is an example
 1320088L,1320089L

Answer 1

使用itertools.chain_fromiterable()先展平嵌套的元组，然后再map()字符串和join()。注意，str()删除L后缀是因为数据不再是type
long。

>>> from itertools import chain
>>> s = ((1320088L,),)
>>> ','.join(map(str,chain.from_iterable(s)))
'1320088'

>>> s = ((1320088L,1232121L),(1320088L,),)
>>> ','.join(map(str,chain.from_iterable(s)))
'1320088,1232121,1320088'

注意，string不是一个好的变量名，因为它与string模块相同。