class praw.models.util.BoundedSet(max_items: int)

A set with a maximum size that evicts the oldest items when necessary.

This class does not implement the complete set interface.

__contains__(item: Any) bool

Test if the BoundedSet contains item.

__init__(max_items: int)

Construct an instance of the BoundedSet.

add(item: Any)

Add an item to the set discarding the oldest item if necessary.

class praw.models.util.ExponentialCounter(max_counter: int)

A class to provide an exponential counter with jitter.

__init__(max_counter: int)

Initialize an instance of ExponentialCounter.



The maximum base value.


The computed value may be 3.125% higher due to jitter.

counter() int

Increment the counter and return the current value with jitter.


Reset the counter to 1.

praw.models.util.permissions_string(permissions: Optional[List[str]], known_permissions: Set[str]) str

Return a comma separated string of permission changes.

  • permissions – A list of strings, or None. These strings can exclusively contain + or - prefixes, or contain no prefixes at all. When prefixed, the resulting string will simply be the joining of these inputs. When not prefixed, all permissions are considered to be additions, and all permissions in the known_permissions set that aren’t provided are considered to be removals. When None, the result is "+all".

  • known_permissions – A set of strings representing the available permissions.

praw.models.util.stream_generator(function: Callable[[Any], Any], pause_after: Optional[int] = None, skip_existing: bool = False, attribute_name: str = 'fullname', exclude_before: bool = False, **function_kwargs: Any) Generator[Any, None, None]

Yield new items from ListingGenerators and None when paused.

  • function – A callable that returns a ListingGenerator, e.g. subreddit.comments or subreddit.new.

  • pause_after – An integer representing the number of requests that result in no new items before this function yields None, effectively introducing a pause into the stream. A negative value yields None after items from a single response have been yielded, regardless of number of new items obtained in that response. A value of 0 yields None after every response resulting in no new items, and a value of None never introduces a pause (default: None).

  • skip_existing – When True does not yield any results from the first request thereby skipping any items that existed in the stream prior to starting the stream (default: False).

  • attribute_name – The field to use as an id (default: “fullname”).

  • exclude_before – When True does not pass params to functions (default: False).

Additional keyword arguments will be passed to function.


This function internally uses an exponential delay with jitter between subsequent responses that contain no new results, up to a maximum delay of just over a 16 seconds. In practice that means that the time before pause for pause_after=N+1 is approximately twice the time before pause for pause_after=N.

For example, to create a stream of comment replies, try:

reply_function = reddit.inbox.comment_replies
for reply in praw.models.util.stream_generator(reply_function):

To pause a comment stream after six responses with no new comments, try:

subreddit = reddit.subreddit("redditdev")
for comment in subreddit.stream.comments(pause_after=6):
    if comment is None:

To resume fetching comments after a pause, try:

subreddit = reddit.subreddit("help")
comment_stream = subreddit.stream.comments(pause_after=5)

for comment in comment_stream:
    if comment is None:
# Do any other processing, then try to fetch more data
for comment in comment_stream:
    if comment is None:

To bypass the internal exponential backoff, try the following. This approach is useful if you are monitoring a subreddit with infrequent activity, and you want the to consistently learn about new items from the stream as soon as possible, rather than up to a delay of just over sixteen seconds.

subreddit = reddit.subreddit("help")
for comment in subreddit.stream.comments(pause_after=0):
    if comment is None: