Iterable Flattener with Depth.

[Pradeep Jindal]

Hi,

5 minute solution to one of my requirements. I wanted to flatten
iterables upto a specific depth.
To be true, didn't search for it on the internet prior to writing this one.


def flatten_iter(my_iter, depth=None):
"""my_iter can be a iterable except string containing nested
iterables upto any depth. This function will flat all
(except string) down to a list containing all the elements in
nested-order.
To add to it you can specify optional depth (int or long)
argument and the
function will flatten the iterable upto that depth (nesting).
"""
if not hasattr(my_iter, '__iter__') or isinstance(my_iter, basestring):
return [my_iter]
elif depth != None and depth <= 0:
return my_iter
temp = []
for x in my_iter:
temp.extend(flatten_iter(x, None if depth == None else depth-1))
return temp

py> temp = [1,[2,[3,4,5],'bash'],6,[7,[8,[9,10,['hi', 'hello']]]], 11, 12]

py> flatten_iter(temp,1)

[1, 2, [3, 4, 5], 'bash', 6, 7, [8, [9, 10, ['hi', 'hello']]], 11, 12]

py> flatten_iter(temp,2)

[1, 2, 3, 4, 5, 'bash', 6, 7, 8, [9, 10, ['hi', 'hello']], 11, 12]

py> flatten_iter(temp)

[1, 2, 3, 4, 5, 'bash', 6, 7, 8, 9, 10, 'hi', 'hello', 11, 12]

py> flatten_iter(temp,3)

[1, 2, 3, 4, 5, 'bash', 6, 7, 8, 9, 10, ['hi', 'hello'], 11, 12]



Any comments?

Thanks
- Pradeep

 

[bearophileHUGS]

Pradeep Jindal:

Any comments?

Something with similar functionality (plus another 20 utility
functions/classes or so) has probably to go into the std lib...

Bye,
bearophile

 

[praddy]

Pradeep Jindal:


Something with similar functionality (plus another 20 utility
functions/classes or so) has probably to go into the std lib...

Bye,
bearophile

Same Here!

- Pradeep

 

[thebjorn]

Same Here!

- Pradeep

Yeah, everyone has to write a flatten sooner or later My version
is at:

http://blog.tkbe.org/archive/python-flatten/

-- bjorn

 

[Ian Clark]

Yeah, everyone has to write a flatten sooner or later My version
is at:

http://blog.tkbe.org/archive/python-flatten/

-- bjorn

And here is mine. Note that it is very similar to Michael Spencer's
implementation[1]. The only difference is that this adds a depth counter.

def iflat(itr, depth=0):
itr = iter(itr)
stack = []
cur_depth = 0

while True:
try:
elem = itr.next()
if hasattr(elem, "__iter__") and cur_depth < depth:
stack.append(itr)
itr = iter(elem)
cur_depth += 1
else:
yield elem
except StopIteration:
if not stack:
raise StopIteration
cur_depth -= 1
itr = stack.pop()


if __name__ == "__main__":
test1 = ((0, 1, 2), ((3, 4), 5), (((6, 7), 8), 9))
test2 = [1,[2,[3,4,5],'bash'],6,[7,[8,[9,10,['hi', 'hello']]]], 11, 12]

for x in (test1, test2):
print
print list(iflat(x))
print
print list(iflat(x, 1))
print list(iflat(x, 2))
print list(iflat(x, 3))
print list(iflat(x, 4))
print iflat(x, 10)

Ian

[1] http://mail.python.org/pipermail/python-list/2005-March/312022.html

 

[Pradeep Jindal]

Yeah, everyone has to write a flatten sooner or later My version
is at:

http://blog.tkbe.org/archive/python-flatten/

-- bjorn

And here is mine. Note that it is very similar to Michael Spencer's
implementation[1]. The only difference is that this adds a depth counter.

def iflat(itr, depth=0):
itr = iter(itr)
stack = []
cur_depth = 0

while True:
try:
elem = itr.next()
if hasattr(elem, "__iter__") and cur_depth < depth:
stack.append(itr)
itr = iter(elem)
cur_depth += 1
else:
yield elem
except StopIteration:
if not stack:
raise StopIteration
cur_depth -= 1
itr = stack.pop()


if __name__ == "__main__":
test1 = ((0, 1, 2), ((3, 4), 5), (((6, 7), 8), 9))
test2 = [1,[2,[3,4,5],'bash'],6,[7,[8,[9,10,['hi', 'hello']]]], 11, 12]

for x in (test1, test2):
print
print list(iflat(x))
print
print list(iflat(x, 1))
print list(iflat(x, 2))
print list(iflat(x, 3))
print list(iflat(x, 4))
print iflat(x, 10)

Ian

[1] http://mail.python.org/pipermail/python-list/2005-March/312022.html

Very nice non-recursive (iterative) implementation of the thing with required
features. Yours is double faster than mine if depth is not specified, Mine is
double faster than yours if depth is specified. And my main aim was the depth
thingy. What do you think?

- Pradeep