Question

I’ve already looked at this question on representing strings in Python but my question is slightly different. It is also different than the question How to concatenate (join) items in a list to a single string which was created after this question and applies to a list of strings and thus does not have any applicability to this question whatsoever (where the thrust of this question is specifically dealing with the challenge of non-string items).

Here’s the code:

>>> class WeirdThing(object):
...     def __init__(self):
...         self.me = time.time()
...     def __str__(self):
...         return "%s" % self.me
...     def __repr__(self):
...         return ";%s;" % self.me
... 
>>> weird_list = [WeirdThing(), WeirdThing(), WeirdThing()]
>>> print weird_list
[;1302217717.89;, ;1302217717.89;, ;1302217717.89;]
>>> "\n".join(weird_list)
Traceback (most recent call last):
  File "<console>", line 1, in <module>
TypeError: sequence item 0: expected string, WeirdThing found

I realize that this works:

>>> "\n".join(str(wi) for wi in weird_list)
'1302217717.89\n1302217717.89\n1302217717.89'
>>> 

Still it would be nice to avoid doing that every time I want to join the objects together. Is it simply not possible?

Answer 1

You have to stringify your objects before you can join them. This is because str.join expects a series of strings, and you must give it a series of strings.

For the sake of less typing at the cost of readability, you can do "\n".join(map(str, list_of_things).