Python: Convert tuple to comma separated String

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,),)

What I found on internet got me till here:

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

what I expect output to look like:

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

Solution 1

Use itertools.chain_fromiterable() to flatten your nested tuples first, then map() to string and join(). Note that str() removes the L suffix because the data is no longer of 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'

Note, string is not a good variable name because it is the same as the string module.

Solution 2

I think the string is a tuple of tuple containing long values.

>>> string = ((1320088L,),)
>>> ','.join(str(y) for x in string for y in x if len(x) > 0)
'1320088'
>>>

e.g. with more than one value

>>> string = ((1320088L,1232121L),(1320088L,),)
>>> ','.join(str(y) for x in string for y in x if len(x) > 0)
'1320088,1232121,1320088'
>>>

Comments

[sirfz]

This answer generalizes well for tuples with length > 1.

[karan_s438]

not sure if @Chris_Rands answer is a better one. This answer and his answer both work for me!

[Chris_Rands]

@JackSparrow these days itertools is the recommended way to flatten lists or tuples stackoverflow.com/questions/952914/…