Could tqdm read my iterator __len__() after __iter__() is called and not before ?

[redorff]

• I have marked all applicable categories:
  • exception-raising bug
  • visual output bug
  • documentation request (i.e. "X is missing from the documentation." If instead I want to ask "how to use X?" I understand StackOverflow#tqdm is more appropriate)
  • new feature request
• I have visited the source website, and in particular
  read the known issues
• I have searched through the issue tracker for duplicates
• I have mentioned version numbers, operating system and
  environment, where applicable:

  import tqdm, sys
  print(tqdm.__version__, sys.version, sys.platform)

4.36.1 3.6.6 (v3.6.6:4cf1f54eb7, Jun 27 2018, 03:37:03) [MSC v.1900 64 bit (AMD64)] win32

Feature request

I created the iterator here below.
My iterator doesn't know its length at init() but only after execution of iter().
tqdm calls len() before iter() is called. So tqdm gets zero as a total.
Is it possible that tqdm could read len() after iter() ?

from tqdm import tqdm
import time

class MyIterator:

    def __init__(self):
        print("called __init__")
        self._search = {} # type: Dict[str, Any]
        self._total = 0 #: total number of results
        self._counter = 0 #: total counter of results

    def __iter__(self):
        print("called __iter__")
        self._search = list(range(12,32))
        self._total = len(self._search)
        self._counter = 0
        return self

    def __next__(self):
        if self._counter >= self._total:
            raise StopIteration
        self._counter += 1
        time.sleep(0.2)
        return self._search.pop(0)

    def __len__(self):
        print("called __len__")
        return self._total

for i in tqdm(MyIterator()):
    pass

Output:

called init
called len
0it [00:00, ?it/s]called iter
20it [00:04, 4.99it/s]

[casperdcl]

I'm not sure this is standard - iterators which only have len() after iter()?

with tqdm(MyIterator()) as t:
    for i in t:
        if not t.total:
            t.total = len(t)
        pass