How to check if tuple has element?

Question

I have an exception from which I'm trying to get args, but if fails.

print hasattr(e, 'args')
print type(e.args)
print hasattr(e.args, '1')
print hasattr(e.args, '0')
print '1' in e.args
print '0' in e.args
print 1 in e.args
print 0 in e.args
print e.args[0]
print e.args[1]

This prints:

True
<type 'tuple'>
False
False
False
False
False
False
Devices not found
4

possible duplicate of [To check whether index of list exists](http://stackoverflow.com/questions/19565745/to-check-whether-index-of-list-exists) — vaultah, Jul 02 '14 at 14:30
I'm not sure what you want. You want to check if `e.args[N]` exists or you want to check if a specific value is part of `e.args`? — netcoder, Jul 02 '14 at 14:32
Just check then length of `e.args`. If `len(e.args) == 1` then `e.args[0]` exists, if `len(e.args) == 2`, then `e.args[1]` exists, and so on. You cannot have empty elements in tuples and they are zero-indexed. — netcoder, Jul 02 '14 at 14:35

Martin Konecny · Answer 1 · 2014-07-02T14:58:29.513

1

You simply use the in operator:

>>> try:
...   raise Exception('spam', 'eggs')
... except Exception as inst:
...   print inst.args
...   print 'spam' in inst.args
... 
('spam', 'eggs')
True

If your code is returning False then most likely 1 wasn't an argument to the exception. Perhaps post the code where the exception was raised.

You can check if the tuple has positions 0 to N by doing len.

edited Jul 02 '14 at 14:58

answered Jul 02 '14 at 14:31

Martin Konecny

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as you can see `print e.args[0]` prints the result so i need to check just if [0] exists or not – Kin Jul 02 '14 at 14:35
Why not check if the `len` of the tuple. Then you know which indexes are present (up to `len-1`) – Martin Konecny Jul 02 '14 at 14:37

score 0 · Answer 2 · edited May 23 '17 at 12:29

You can check the length of your tuple:

t = 1, 2, 3,
if len(t) >= 1:
    value = t[0]    # no error there

...or you can just check for an IndexError, which I'd say is more pythonic:

t = 1, 2, 3,
try:
    value = t[4]
except IndexError:
    # handle error case
    pass

The latter is a concept named EAFP: Easier to ask for forgiveness than permission, which is a well known and common Python coding style.

How to check if tuple has element?

2 Answers2