How to Determine the Status of Empty Generators in Python?

Knowing the Status of Empty Generators

Knowing upfront if a generator is empty can greatly simplify certain codepaths. Unfortunately, generators don't provide a straightforward method like peek, hasNext, or isEmpty to determine this.

Suggestion:

To work around this, you can create a peek function to do this manually.

<code class="python">def peek(iterable):
    try:
        first = next(iterable)
    except StopIteration:
        return None
    return first, itertools.chain([first], iterable)</code>

Usage:

Once you have the peek function, you can use it like this:

<code class="python">res = peek(mysequence)
if res is None:
    # sequence is empty.  Do stuff.
else:
    first, mysequence = res
    # Do something with first, maybe?
    # Then iterate over the sequence:
    for element in mysequence:
        # etc.</code>

This approach lets you effectively handle empty generators without having to traverse the entire sequence.

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