How to denest tuples in Python

Question

I have a tuple of tuples. Each tuple within the tuple can be itself a tuple of tuple with no particular limitation in the nesting.

I would like to flatten this into a single tuple containing all the elements in the same order than a print would print them on screen.

For example:

a = ( 1 , (2, 3), (4, (5), (6, 7, (8, 9))))

would become:

( 1 , 2, 3, 4, 5, 6, 7, 8, 9 )

I may be wrong but I have not seen the same question. I am quite new to Python so I do not know if there is a Python way to do this (I would have gone for a generator personally).

got it, I voted to close, it is indeed similar. Thanks. – BlueTrin Jan 04 '14 at 17:32 — BlueTrin, Jan 04 '14 at 17:32

shx2 · Accepted Answer · 2014-01-04T17:32:13.920

2

You can use a recusive flattening function:

def flatten(seq):
  for x in seq:
    if isinstance(x, basestring):  # use isinstance(x, str) in python3
       yield x
       continue
    try:
      # in python >=3.3, can use the nifty "yield from", like: yield from flatten(x)
      for y in flatten(x):
        yield y
    except TypeError:
       yield x  # not iterable

print tuple(flatten(a))
=> (1, 2, 3, 4, 5, 6, 7, 8, 9)

Please note that in your initialisation of a, (5) is equivalent to 5. What you probably meant is a tuple of size 1, which is created using a comma, like: (5,).

edited Jan 04 '14 at 17:32

answered Jan 04 '14 at 17:18

shx2

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This doesn't work for strings. – Jan 04 '14 at 17:22
@delnan: in fact I gave a bad example, I have strings in my tuple. It seems to complain about the number of recursions because the strings are fairly long and I suspect it is trying to create the iterator letter by letter – BlueTrin Jan 04 '14 at 17:29
I vote to close my question. someone found a duplicate ? – BlueTrin Jan 04 '14 at 17:31
2

@BlueTrin Worse, it recurses infinitely if any (non-empty) string is encountered: Iterating a string yields one-character strings, and iterating those again yields one-character strings (one, to be precise), and so on without end. – Jan 04 '14 at 17:32

RGS · Answer 2 · 2014-01-04T17:34:44.277

1

You can use this recursive function:

a = ( 1 , (2, 3), (4, (5), (6, 7, (8, 9))))
b = []
def tup(x):
    if not(type(x) == tuple):
        b.append(x)
    else:
        for i in range(len(x)):
            tup(x[i])

tup(a)
print(b)

edited Jan 04 '14 at 17:34

answered Jan 04 '14 at 17:29

RGS

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That doesn't work. At all. – Jan 04 '14 at 17:33
Just worked with me --' – RGS Jan 04 '14 at 17:33
@delnan edited, had an error there... sry, and thanks – RGS Jan 04 '14 at 17:35

How to denest tuples in Python

2 Answers2