Connection Pools

class urllib3.HTTPConnectionPool(host, port=None, timeout=_TYPE_DEFAULT.token, maxsize=1, block=False, headers=None, retries=None, _proxy=None, _proxy_headers=None, _proxy_config=None, **conn_kw)

Bases: ConnectionPool, RequestMethods

Thread-safe connection pool for one host.

  • host (str) – Host used for this HTTP Connection (e.g. “localhost”), passed into http.client.HTTPConnection.

  • port (int | None) – Port used for this HTTP Connection (None is equivalent to 80), passed into http.client.HTTPConnection.

  • timeout (_TYPE_TIMEOUT | None) – Socket timeout in seconds for each individual connection. This can be a float or integer, which sets the timeout for the HTTP request, or an instance of urllib3.util.Timeout which gives you more fine-grained control over request timeouts. After the constructor has been parsed, this is always a urllib3.util.Timeout object.

  • maxsize (int) – Number of connections to save that can be reused. More than 1 is useful in multithreaded situations. If block is set to False, more connections will be created but they will not be saved once they’ve been used.

  • block (bool) – If set to True, no more than maxsize connections will be used at a time. When no free connections are available, the call will block until a connection has been released. This is a useful side effect for particular multithreaded situations where one does not want to use more than maxsize connections per host to prevent flooding.

  • headers (Mapping[str, str] | None) – Headers to include with all requests, unless other headers are given explicitly.

  • retries (Retry | bool | int | None) – Retry configuration to use by default with requests in this pool.

  • _proxy (Url | None) – Parsed proxy URL, should not be used directly, instead, see urllib3.ProxyManager

  • _proxy_headers (Mapping[str, str] | None) – A dictionary with proxy headers, should not be used directly, instead, see urllib3.ProxyManager

  • **conn_kw (Any) – Additional parameters are used to create fresh urllib3.connection.HTTPConnection, urllib3.connection.HTTPSConnection instances.

  • _proxy_config (ProxyConfig | None)

  • **conn_kw


alias of HTTPConnection


Close all pooled connections and disable the pool.

Return type:



Check if the given url is a member of the same host as this connection pool.


url (str)

Return type:


scheme: str | None = 'http'
urlopen(method, url, body=None, headers=None, retries=None, redirect=True, assert_same_host=True, timeout=_TYPE_DEFAULT.token, pool_timeout=None, release_conn=None, chunked=False, body_pos=None, preload_content=True, decode_content=True, **response_kw)

Get a connection from the pool and perform an HTTP request. This is the lowest level call for making a request, so you’ll need to specify all the raw details.


More commonly, it’s appropriate to use a convenience method such as request().


release_conn will only behave as expected if preload_content=False because we want to make preload_content=False the default behaviour someday soon without breaking backwards compatibility.

  • method (str) – HTTP request method (such as GET, POST, PUT, etc.)

  • url (str) – The URL to perform the request on.

  • body (bytes | IO[Any] | Iterable[bytes] | str | None) – Data to send in the request body, either str, bytes, an iterable of str/bytes, or a file-like object.

  • headers (Mapping[str, str] | None) – Dictionary of custom headers to send, such as User-Agent, If-None-Match, etc. If None, pool headers are used. If provided, these headers completely replace any pool-specific headers.

  • retries (Retry, False, or an int.) –

    Configure the number of retries to allow before raising a MaxRetryError exception.

    If None (default) will retry 3 times, see Retry.DEFAULT. Pass a Retry object for fine-grained control over different types of retries. Pass an integer number to retry connection errors that many times, but no other types of errors. Pass zero to never retry.

    If False, then retries are disabled and any exception is raised immediately. Also, instead of raising a MaxRetryError on redirects, the redirect response will be returned.

  • redirect (bool) – If True, automatically handle redirects (status codes 301, 302, 303, 307, 308). Each redirect counts as a retry. Disabling retries will disable redirect, too.

  • assert_same_host (bool) – If True, will make sure that the host of the pool requests is consistent else will raise HostChangedError. When False, you can use the pool on an HTTP proxy and request foreign hosts.

  • timeout (Timeout | float | _TYPE_DEFAULT | None) – If specified, overrides the default timeout for this one request. It may be a float (in seconds) or an instance of urllib3.util.Timeout.

  • pool_timeout (int | None) – If set and the pool is set to block=True, then this method will block for pool_timeout seconds and raise EmptyPoolError if no connection is available within the time period.

  • preload_content (bool) – If True, the response’s body will be preloaded into memory.

  • decode_content (bool) – If True, will attempt to decode the body based on the ‘content-encoding’ header.

  • release_conn (bool | None) – If False, then the urlopen call will not release the connection back into the pool once a response is received (but will release if you read the entire contents of the response such as when preload_content=True). This is useful if you’re not preloading the response’s content immediately. You will need to call r.release_conn() on the response r to return the connection back into the pool. If None, it takes the value of preload_content which defaults to True.

  • chunked (bool) – If True, urllib3 will send the body using chunked transfer encoding. Otherwise, urllib3 will send the body using the standard content-length form. Defaults to False.

  • body_pos (int) – Position to seek to in file-like body in the event of a retry or redirect. Typically this won’t need to be set because urllib3 will auto-populate the value when needed.

  • response_kw (Any)

Return type:


class urllib3.HTTPSConnectionPool(host, port=None, timeout=_TYPE_DEFAULT.token, maxsize=1, block=False, headers=None, retries=None, _proxy=None, _proxy_headers=None, key_file=None, cert_file=None, cert_reqs=None, key_password=None, ca_certs=None, ssl_version=None, ssl_minimum_version=None, ssl_maximum_version=None, assert_hostname=None, assert_fingerprint=None, ca_cert_dir=None, **conn_kw)

Bases: HTTPConnectionPool

Same as HTTPConnectionPool, but HTTPS.

HTTPSConnection uses one of assert_fingerprint, assert_hostname and host in this order to verify connections. If assert_hostname is False, no verification is done.

The key_file, cert_file, cert_reqs, ca_certs, ca_cert_dir, ssl_version, key_password are only used if ssl is available and are fed into urllib3.util.ssl_wrap_socket() to upgrade the connection socket into an SSL socket.


alias of HTTPSConnection

scheme: str | None = 'https'
class urllib3.connectionpool.ConnectionPool(host, port=None)

Bases: object

Base class for all connection pools, such as HTTPConnectionPool and HTTPSConnectionPool.


ConnectionPool.urlopen() does not normalize or percent-encode target URIs which is useful if your target server doesn’t support percent-encoded target URIs.

  • host (str)

  • port (int | None)


alias of LifoQueue


Close all pooled connections and disable the pool.

Return type:


scheme: str | None = None
urllib3.connectionpool.connection_from_url(url, **kw)

Given a url, return an ConnectionPool instance of its host.

This is a shortcut for not having to parse out the scheme, host, and port of the url before creating an ConnectionPool instance.

  • url (str) – Absolute URL string that must include the scheme. Port is optional.

  • **kw (Any) – Passes additional parameters to the constructor of the appropriate ConnectionPool. Useful for specifying things like timeout, maxsize, headers, etc.

Return type:



>>> conn = connection_from_url('')
>>> r = conn.request('GET', '/')