.. _callbacks: Callbacks ========= For more fine-grained control, libcurl allows a number of callbacks to be associated with each connection. In pycurl, callbacks are defined using the ``setopt()`` method for Curl objects with options ``WRITEFUNCTION``, ``READFUNCTION``, ``HEADERFUNCTION``, ``PROGRESSFUNCTION``, ``XFERINFOFUNCTION``, ``IOCTLFUNCTION``, ``DEBUGFUNCTION``, ``PREREQFUNCTION``, ``TRAILERFUNCTION``, ``RESOLVER_START_FUNCTION``, ``FNMATCH_FUNCTION``, ``HSTSREADFUNCTION`` or ``HSTSWRITEFUNCTION``. These options correspond to the libcurl options with ``CURLOPT_`` prefix removed. A callback in pycurl must be either a regular Python function, a class method or an extension type function. There are some limitations to some of the options which can be used concurrently with the pycurl callbacks compared to the libcurl callbacks. This is to allow different callback functions to be associated with different Curl objects. More specifically, ``WRITEDATA`` cannot be used with ``WRITEFUNCTION``, ``READDATA`` cannot be used with ``READFUNCTION``, ``WRITEHEADER`` cannot be used with ``HEADERFUNCTION``. In practice, these limitations can be overcome by having a callback function be a class instance method and rather use the class instance attributes to store per object data such as files used in the callbacks. The signature of each callback used in PycURL is documented below. Error Reporting --------------- PycURL callbacks are invoked as follows: Python application -> ``perform()`` -> libcurl (C code) -> Python callback Because callbacks are invoked by libcurl, they should not raise exceptions on failure but instead return appropriate values indicating failure. The documentation for individual callbacks below specifies expected success and failure return values. Unhandled exceptions propagated out of Python callbacks will be intercepted by PycURL or the Python runtime. This will fail the callback with a generic failure status, in turn failing the ``perform()`` operation. A failing ``perform()`` will raise ``pycurl.error``, but the error code used depends on the specific callback. ``KeyboardInterrupt`` and other ``BaseException`` subclasses (for example, ``SystemExit``) are handled specially: if they are raised inside a callback, they are preserved and re-raised to the caller instead of being converted into a ``pycurl.error``. Rich context information like exception objects can be stored in various ways, for example the following example stores OPENSOCKET callback exception on the Curl object:: import pycurl, random, socket class ConnectionRejected(Exception): pass def opensocket(curl, purpose, curl_address): # always fail curl.exception = ConnectionRejected('Rejecting connection attempt in opensocket callback') return pycurl.SOCKET_BAD # the callback must create a socket if it does not fail, # see examples/opensocketexception.py c = pycurl.Curl() c.setopt(c.URL, 'http://pycurl.io') c.exception = None c.setopt(c.OPENSOCKETFUNCTION, lambda purpose, address: opensocket(c, purpose, address)) try: c.perform() except pycurl.error as e: if e.args[0] == pycurl.E_COULDNT_CONNECT and c.exception: print(c.exception) else: print(e) WRITEFUNCTION ------------- .. function:: WRITEFUNCTION(byte string) -> number of characters written Callback for writing data. Corresponds to `CURLOPT_WRITEFUNCTION`_ in libcurl. On Python 3, the argument is of type ``bytes``. The ``WRITEFUNCTION`` callback may return the number of bytes written. If this number is not equal to the size of the byte string, this signifies an error and libcurl will abort the request. Returning ``None`` is an alternate way of indicating that the callback has consumed all of the string passed to it and, hence, succeeded. Passing ``use_memoryview=True`` to ``Curl.setopt`` causes the callback to receive a read-only ``memoryview`` over libcurl's temporary buffer instead of a ``bytes`` copy. The memoryview is released as soon as the callback returns, so any reference kept past that point raises ``ValueError`` on access. Example:: def write_cb(chunk: memoryview) -> int: return len(chunk) curl.setopt(pycurl.WRITEFUNCTION, write_cb, use_memoryview=True) `write_test.py test`_ shows how to use ``WRITEFUNCTION``. Example: Callbacks for document header and body ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This example prints the header data to stderr and the body data to stdout. Also note that neither callback returns the number of bytes written. For WRITEFUNCTION and HEADERFUNCTION callbacks, returning None implies that all bytes where written. :: ## Callback function invoked when body data is ready def body(buf): # Print body data to stdout import sys sys.stdout.write(buf) # Returning None implies that all bytes were written ## Callback function invoked when header data is ready def header(buf): # Print header data to stderr import sys sys.stderr.write(buf) # Returning None implies that all bytes were written c = pycurl.Curl() c.setopt(pycurl.URL, "http://www.python.org/") c.setopt(pycurl.WRITEFUNCTION, body) c.setopt(pycurl.HEADERFUNCTION, header) c.perform() HEADERFUNCTION -------------- .. function:: HEADERFUNCTION(byte string) -> number of characters written Callback for writing received headers. Corresponds to `CURLOPT_HEADERFUNCTION`_ in libcurl. On Python 3, the argument is of type ``bytes``. The ``HEADERFUNCTION`` callback may return the number of bytes written. If this number is not equal to the size of the byte string, this signifies an error and libcurl will abort the request. Returning ``None`` is an alternate way of indicating that the callback has consumed all of the string passed to it and, hence, succeeded. Passing ``use_memoryview=True`` to ``Curl.setopt`` causes the callback to receive a read-only ``memoryview`` over libcurl's temporary buffer instead of a ``bytes`` copy. The memoryview is released as soon as the callback returns, so any reference kept past that point raises ``ValueError`` on access. Example:: def header_cb(chunk: memoryview) -> int: return len(chunk) curl.setopt(pycurl.HEADERFUNCTION, header_cb, use_memoryview=True) `header_test.py test`_ shows how to use ``WRITEFUNCTION``. READFUNCTION ------------ .. function:: READFUNCTION(number of characters to read) -> byte string Callback for reading data. Corresponds to `CURLOPT_READFUNCTION`_ in libcurl. The callback must return either a C-contiguous object supporting the buffer protocol (e.g. `bytes`, `bytearray`, `memoryview`, or a C-contiguous `numpy` array) or a Unicode string consisting of ASCII code points only. In addition, ``READFUNCTION`` may return ``READFUNC_ABORT`` or ``READFUNC_PAUSE``. See the libcurl documentation for an explanation of these values. The `file_upload.py example`_ in the distribution contains example code for using ``READFUNCTION``. .. _SEEKFUNCTION: SEEKFUNCTION ------------ .. function:: SEEKFUNCTION(offset, origin) -> status Callback for seek operations. Corresponds to `CURLOPT_SEEKFUNCTION`_ in libcurl. ``origin`` is ``0`` (beginning), ``1`` (current position) or ``2`` (end). Return one of: - ``SEEKFUNC_OK`` (seek succeeded) - ``SEEKFUNC_FAIL`` (hard failure) - ``SEEKFUNC_CANTSEEK`` (seek not possible; libcurl may fall back) IOCTLFUNCTION ------------- .. function:: IOCTLFUNCTION(ioctl cmd) -> status Callback for I/O operations. Corresponds to `CURLOPT_IOCTLFUNCTION`_ in libcurl. *Note:* this callback is deprecated. Use :ref:`SEEKFUNCTION ` instead. DEBUGFUNCTION ------------- .. function:: DEBUGFUNCTION(debug message type, debug message byte string) -> None Callback for debug information. Corresponds to `CURLOPT_DEBUGFUNCTION`_ in libcurl. *Changed in version 7.19.5.2:* The second argument to a ``DEBUGFUNCTION`` callback is now of type ``bytes`` on Python 3. Previously the argument was of type ``str``. `debug_test.py test`_ shows how to use ``DEBUGFUNCTION``. Example: Debug callbacks ~~~~~~~~~~~~~~~~~~~~~~~~ This example shows how to use the debug callback. The debug message type is an integer indicating the type of debug message. The VERBOSE option must be enabled for this callback to be invoked. :: def test(debug_type, debug_msg): print("debug(%d): %s" % (debug_type, debug_msg)) c = pycurl.Curl() c.setopt(pycurl.URL, "https://curl.haxx.se/") c.setopt(pycurl.VERBOSE, 1) c.setopt(pycurl.DEBUGFUNCTION, test) c.perform() PROGRESSFUNCTION ---------------- .. function:: PROGRESSFUNCTION(download total, downloaded, upload total, uploaded) -> status Callback for progress meter. Corresponds to `CURLOPT_PROGRESSFUNCTION`_ in libcurl. ``PROGRESSFUNCTION`` receives amounts as floating point arguments to the callback. Since libcurl 7.32.0 ``PROGRESSFUNCTION`` is deprecated; ``XFERINFOFUNCTION`` should be used instead which receives amounts as long integers. ``NOPROGRESS`` option must be set for False libcurl to invoke a progress callback, as PycURL by default sets ``NOPROGRESS`` to True. XFERINFOFUNCTION ---------------- .. function:: XFERINFOFUNCTION(download total, downloaded, upload total, uploaded) -> status Callback for progress meter. Corresponds to `CURLOPT_XFERINFOFUNCTION`_ in libcurl. ``XFERINFOFUNCTION`` receives amounts as long integers. ``NOPROGRESS`` option must be set for False libcurl to invoke a progress callback, as PycURL by default sets ``NOPROGRESS`` to True. Example: Download/upload progress callback ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This example shows how to use the progress callback. When downloading a document, the arguments related to uploads are zero, and vice versa. :: ## Callback function invoked when download/upload has progress def progress(download_t, download_d, upload_t, upload_d): print("Total to download", download_t) print("Total downloaded", download_d) print("Total to upload", upload_t) print("Total uploaded", upload_d) c = pycurl.Curl() c.setopt(c.URL, "http://slashdot.org/") c.setopt(c.NOPROGRESS, False) c.setopt(c.XFERINFOFUNCTION, progress) c.perform() OPENSOCKETFUNCTION ------------------ .. function:: OPENSOCKETFUNCTION(purpose, address) -> int Callback for opening sockets. Corresponds to `CURLOPT_OPENSOCKETFUNCTION`_ in libcurl. *purpose* is a ``SOCKTYPE_*`` value. *address* is a `namedtuple`_ with ``family``, ``socktype``, ``protocol`` and ``addr`` fields, per `CURLOPT_OPENSOCKETFUNCTION`_ documentation. *addr* is an object representing the address. Currently the following address families are supported: - ``AF_INET``: *addr* is a 2-tuple of ``(host, port)``. - ``AF_INET6``: *addr* is a 4-tuple of ``(host, port, flow info, scope id)``. - ``AF_UNIX``: *addr* is a byte string containing path to the Unix socket. Availability: Unix. This behavior matches that of Python's `socket module`_. The callback should return a socket object, a socket file descriptor or a Python object with a ``fileno`` property containing the socket file descriptor. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. `open_socket_cb_test.py test`_ shows how to use ``OPENSOCKETFUNCTION``. *Changed in version 7.21.5:* Previously, the callback received ``family``, ``socktype``, ``protocol`` and ``addr`` parameters (``purpose`` was not passed and ``address`` was flattened). Also, ``AF_INET6`` addresses were exposed as 2-tuples of ``(host, port)`` rather than 4-tuples. *Changed in version 7.19.3:* ``addr`` parameter added to the callback. CLOSESOCKETFUNCTION ------------------- .. function:: CLOSESOCKETFUNCTION(curlfd) -> int Callback for setting socket options. Corresponds to `CURLOPT_CLOSESOCKETFUNCTION`_ in libcurl. *curlfd* is the file descriptor to be closed. The callback should return an ``int``. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. `close_socket_cb_test.py test`_ shows how to use ``CLOSESOCKETFUNCTION``. SOCKOPTFUNCTION --------------- .. function:: SOCKOPTFUNCTION(curlfd, purpose) -> int Callback for setting socket options. Corresponds to `CURLOPT_SOCKOPTFUNCTION`_ in libcurl. *curlfd* is the file descriptor of the newly created socket. *purpose* is a ``SOCKTYPE_*`` value. The callback should return an ``int``. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. `sockopt_cb_test.py test`_ shows how to use ``SOCKOPTFUNCTION``. SSH_KEYFUNCTION --------------- .. function:: SSH_KEYFUNCTION(known_key, found_key, match) -> int Callback for known host matching logic. Corresponds to `CURLOPT_SSH_KEYFUNCTION`_ in libcurl. *known_key* and *found_key* are instances of ``KhKey`` class which is a `namedtuple`_ with ``key`` and ``keytype`` fields, corresponding to libcurl's ``struct curl_khkey``:: KhKey = namedtuple('KhKey', ('key', 'keytype')) The *key* field of ``KhKey`` is ``bytes``. *keytype* is an ``int``. *known_key* may be ``None`` when there is no known matching host key. ``SSH_KEYFUNCTION`` callback should return a ``KHSTAT_*`` value. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. `ssh_key_cb_test.py test`_ shows how to use ``SSH_KEYFUNCTION``. TIMERFUNCTION ------------- .. function:: TIMERFUNCTION(timeout_ms) -> int | None Callback for installing a timer requested by libcurl. Corresponds to `CURLMOPT_TIMERFUNCTION`_. The application should arrange for a non-repeating timer to fire in ``timeout_ms`` milliseconds, at which point the application should call either :ref:`socket_action ` or :ref:`perform `. See the `CURLMOPT_TIMERFUNCTION`_ docs for the special values of ``timeout_ms``. Return ``0`` or ``None`` for success, or ``-1`` to abort all in-progress transfers in the multi handle. Exceptions raised in the callback are printed to stderr and treated as ``-1``. See ``examples/multi-socket_action-select.py`` for an example program that uses the timer function and the socket function. Asyncio applications can use :py:class:`pycurl.AsyncCurlMulti` instead of installing these callbacks directly. SOCKETFUNCTION -------------- .. function:: SOCKETFUNCTION(what, sock_fd, multi, socketp) -> int | None Callback notifying the application about activity on libcurl sockets. Corresponds to `CURLMOPT_SOCKETFUNCTION`_. Note that the PycURL callback takes ``what`` as the first argument and ``sock_fd`` as the second argument, whereas the libcurl callback takes ``sock_fd`` as the first argument and ``what`` as the second argument. *what* is one of ``pycurl.POLL_IN``, ``POLL_OUT``, ``POLL_INOUT`` or ``POLL_REMOVE``; see the `CURLMOPT_SOCKETFUNCTION`_ docs for their meaning. The ``userp`` ("private callback pointer") argument, as described in the ``CURLMOPT_SOCKETFUNCTION`` documentation, is set to the ``CurlMulti`` instance. The ``socketp`` ("private socket pointer") argument, as described in the ``CURLMOPT_SOCKETFUNCTION`` documentation, is set to the value provided to the :ref:`assign ` method for the corresponding ``sock_fd``, or ``None`` if no value was assigned. Return ``0`` or ``None`` for success, or ``-1`` to abort all in-progress transfers in the multi handle. Exceptions raised in the callback are printed to stderr and treated as ``-1``. See ``examples/multi-socket_action-select.py`` for an example program that uses the timer function and the socket function. Asyncio applications can use :py:class:`pycurl.AsyncCurlMulti` instead of installing these callbacks directly. NOTIFYFUNCTION -------------- .. function:: NOTIFYFUNCTION(notification, curl) -> None Callback receiving libcurl multi notifications. Requires libcurl 8.17.0 or later. Corresponds to `CURLMOPT_NOTIFYFUNCTION`_. *notification* is one of ``pycurl.M_NOTIFY_INFO_READ`` (the multi info-read queue became non-empty) or ``pycurl.M_NOTIFY_EASY_DONE`` (one easy handle finished). ``M_NOTIFY_EASY_DONE`` does not carry the ``CURLcode`` result, so applications that need success or failure information must still drain ``info_read``. *curl* is the original ``pycurl.Curl`` object the notification is about, or ``None`` when PyCURL cannot safely identify it. Install the callback with ``setopt(M_NOTIFYFUNCTION, ...)``. Turn individual notifications on or off with :py:meth:`notify_enable ` and :py:meth:`notify_disable `. Calling ``info_read`` from inside the callback is supported and is the intended pattern for ``M_NOTIFY_INFO_READ``. The return value is ignored (the C callback returns ``void``). Exceptions raised in the callback are printed to stderr and do not abort transfers. PREREQFUNCTION --------------- .. function:: PREREQFUNCTION(conn_primary_ip, conn_local_ip, conn_primary_port, conn_local_port) -> int Callback called when a connection has been established, but before a request has been made. Corresponds to `CURLOPT_PREREQFUNCTION`_ in libcurl. *conn_primary_ip* is the primary IP address of the remote server established with this connection (as a string). *conn_local_ip* is the originating IP address for this connection (as a string). *conn_primary_port* is the primary port number on the remote server established with this connection. *conn_local_port* is the originating port number for this connection. The callback should return an ``int``, which must be either ``PREREQFUNC_OK`` (on success) or ``PREREQFUNC_ABORT`` to cause the transfer to fail with result ``ABORTED_BY_CALLBACK``. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. `prereq_cb_test.py test`_ shows how to use ``PREREQFUNCTION``. TRAILERFUNCTION --------------- .. function:: TRAILERFUNCTION() -> list of strings or None Callback for supplying HTTP trailing headers on chunked uploads. Corresponds to `CURLOPT_TRAILERFUNCTION`_ in libcurl. The callback takes no arguments and should return either ``None`` (no trailing headers) or a list or tuple of header strings in ``"Name: value"`` form. The same rules apply to these strings as do to ``HTTPHEADER`` entries. Raising an exception from the callback, or returning any other type, causes the transfer to fail with ``TRAILERFUNC_ABORT``. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. RESOLVER_START_FUNCTION ----------------------- .. function:: RESOLVER_START_FUNCTION() -> int Callback invoked before each name resolution. Corresponds to `CURLOPT_RESOLVER_START_FUNCTION`_ in libcurl. The callback takes no arguments. Return ``0`` (or ``None``) to let the resolution proceed; return any non-zero value to abort the transfer. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. FNMATCH_FUNCTION ---------------- .. function:: FNMATCH_FUNCTION(pattern, string) -> int Callback for wildcard matching used by the FTP wildcard transfer feature. Corresponds to `CURLOPT_FNMATCH_FUNCTION`_ in libcurl. *pattern* and *string* are both ``bytes``. The callback should return one of: - ``FNMATCHFUNC_MATCH`` (pattern matched) - ``FNMATCHFUNC_NOMATCH`` (pattern did not match) - ``FNMATCHFUNC_FAIL`` (error during matching; aborts the transfer) The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. HSTSWRITEFUNCTION ----------------- .. function:: HSTSWRITEFUNCTION(entry, idx) -> int Callback for persisting the in-memory HSTS cache. Corresponds to `CURLOPT_HSTSWRITEFUNCTION`_ in libcurl. Requires ``HSTS_CTRL`` to be set to ``CURLHSTS_ENABLE``. *entry* is an ``HstsEntry`` `namedtuple`_ with ``host``, ``expire`` and ``include_subdomains`` fields:: HstsEntry = namedtuple('HstsEntry', ('host', 'expire', 'include_subdomains')) *host* is ``bytes``. *expire* is a tz-aware ``datetime`` in UTC, or ``None`` when the entry never expires. *include_subdomains* is ``bool``. *idx* is an ``HstsIndex`` `namedtuple`_ indicating progress through the cache:: HstsIndex = namedtuple('HstsIndex', ('idx', 'total')) The callback should return ``CURLSTS_OK`` (entry accepted), ``CURLSTS_DONE`` (stop iterating) or ``CURLSTS_FAIL`` (error). Returning ``None`` is equivalent to ``CURLSTS_OK``. libcurl invokes the callback during ``perform()`` and during handle cleanup; exceptions raised inside the callback while the handle is being cleaned up are written to :py:data:`sys.unraisablehook` and do not propagate. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. HSTSREADFUNCTION ---------------- .. function:: HSTSREADFUNCTION() -> HstsEntry or None Callback for preloading the in-memory HSTS cache. Corresponds to `CURLOPT_HSTSREADFUNCTION`_ in libcurl. Requires ``HSTS_CTRL`` to be set to ``CURLHSTS_ENABLE``. The callback takes no arguments. It is invoked repeatedly until it returns ``None``. Return ``None`` to signal there are no more entries (``CURLSTS_DONE``), or an ``HstsEntry`` (or any 3-tuple) where: - *host* is ``bytes`` or an ASCII ``str``. - *expire* is a ``datetime`` or ``None``. ``None`` means the entry never expires. Aware datetimes are converted to UTC; naive datetimes are interpreted as UTC. - *include_subdomains* is any truthy/falsy value. Raising an exception or returning anything else causes the transfer to fail with ``CURLSTS_FAIL``. The callback may be unset by calling :ref:`setopt ` with ``None`` as the value or by calling :ref:`unsetopt `. WebSocket callback receive (libcurl 7.86.0 or later) ---------------------------------------------------- libcurl supports two WebSocket usage models: *detached mode* (``CONNECT_ONLY=2`` plus ``ws_send`` / ``ws_recv``, documented on the :ref:`Curl object `) and *callback-receive mode*, where libcurl drives the transfer and delivers each received frame chunk through the ordinary ``WRITEFUNCTION`` callback. No separate callback registration is required — set ``WRITEFUNCTION`` on a ``ws://`` / ``wss://`` URL, leave ``CONNECT_ONLY`` unset, and call :ref:`perform ` as you would for any other transfer. ``perform()`` blocks for the full lifetime of the WebSocket connection and returns when the peer closes (or the transfer otherwise terminates), so the server side must have a predictable end condition. Inside the callback, :py:meth:`pycurl.Curl.ws_meta` returns a ``WsFrame`` namedtuple (``age``, ``flags``, ``offset``, ``bytesleft``, ``len``) describing the chunk currently being delivered. The ``flags`` field is a bitmask of ``WS_TEXT``, ``WS_BINARY``, ``WS_CONT``, ``WS_PING``, ``WS_PONG``, ``WS_CLOSE``, and ``WS_OFFSET``. libcurl's ``curl_ws_meta()`` returns ``NULL`` outside the valid callback context; PycURL maps that to Python ``None``. The same ``ws_meta()`` method is safe to call after ``perform()`` has returned (it simply returns ``None``) and in detached mode (likewise). Calling :py:meth:`ws_send` or :py:meth:`ws_close` from inside the ``WRITEFUNCTION`` is allowed: libcurl treats the call as a blocking send and returns only once the frame has been fully written (or an error occurs). ``CURLE_AGAIN`` / ``BlockingIOError`` semantics do not apply in this context. That relaxation applies only inside the callback itself; calls from another thread while ``perform()`` is running are still rejected. :py:meth:`ws_recv` and :py:meth:`ws_recv_into` remain detached-only and still raise ``pycurl.error`` while ``perform()`` is running. Example:: import pycurl c = pycurl.Curl() def on_ws_chunk(data): meta = c.ws_meta() # valid only inside this callback if meta is not None and meta.flags & pycurl.WS_TEXT: print("text chunk:", data) c.ws_send(b"ack", pycurl.WS_BINARY) # blocking send return len(data) c.setopt(c.URL, "wss://example.com/socket") c.setopt(c.WRITEFUNCTION, on_ws_chunk) c.perform() # blocks until peer closes c.close() `ws_callback.py example`_ is a complete runnable version. .. _CURLOPT_HEADERFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_HEADERFUNCTION.html .. _CURLOPT_WRITEFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_WRITEFUNCTION.html .. _CURLOPT_READFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_READFUNCTION.html .. _CURLOPT_PROGRESSFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_PROGRESSFUNCTION.html .. _CURLOPT_XFERINFOFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_XFERINFOFUNCTION.html .. _CURLOPT_DEBUGFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_DEBUGFUNCTION.html .. _CURLOPT_SEEKFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_SEEKFUNCTION.html .. _CURLOPT_IOCTLFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_IOCTLFUNCTION.html .. _file_upload.py example: https://github.com/pycurl/pycurl/blob/master/examples/file_upload.py .. _write_test.py test: https://github.com/pycurl/pycurl/blob/master/tests/write_test.py .. _header_test.py test: https://github.com/pycurl/pycurl/blob/master/tests/header_test.py .. _debug_test.py test: https://github.com/pycurl/pycurl/blob/master/tests/debug_test.py .. _CURLOPT_SSH_KEYFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_SSH_KEYFUNCTION.html .. _namedtuple: https://docs.python.org/library/collections.html#collections.namedtuple .. _CURLOPT_SOCKOPTFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_SOCKOPTFUNCTION.html .. _sockopt_cb_test.py test: https://github.com/pycurl/pycurl/blob/master/tests/sockopt_cb_test.py .. _ssh_key_cb_test.py test: https://github.com/pycurl/pycurl/blob/master/tests/ssh_key_cb_test.py .. _CURLOPT_CLOSESOCKETFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_CLOSESOCKETFUNCTION.html .. _close_socket_cb_test.py test: https://github.com/pycurl/pycurl/blob/master/tests/close_socket_cb_test.py .. _CURLOPT_OPENSOCKETFUNCTION: https://curl.haxx.se/libcurl/c/CURLOPT_OPENSOCKETFUNCTION.html .. _open_socket_cb_test.py test: https://github.com/pycurl/pycurl/blob/master/tests/open_socket_cb_test.py .. _socket module: https://docs.python.org/library/socket.html .. _CURLMOPT_TIMERFUNCTION: https://curl.se/libcurl/c/CURLMOPT_TIMERFUNCTION.html .. _CURLMOPT_SOCKETFUNCTION: https://curl.se/libcurl/c/CURLMOPT_SOCKETFUNCTION.html .. _CURLMOPT_NOTIFYFUNCTION: https://curl.se/libcurl/c/CURLMOPT_NOTIFYFUNCTION.html .. _CURLOPT_PREREQFUNCTION: https://curl.se/libcurl/c/CURLOPT_PREREQFUNCTION.html .. _prereq_cb_test.py test: https://github.com/pycurl/pycurl/blob/master/tests/prereq_cb_test.py .. _CURLOPT_TRAILERFUNCTION: https://curl.se/libcurl/c/CURLOPT_TRAILERFUNCTION.html .. _CURLOPT_RESOLVER_START_FUNCTION: https://curl.se/libcurl/c/CURLOPT_RESOLVER_START_FUNCTION.html .. _CURLOPT_FNMATCH_FUNCTION: https://curl.se/libcurl/c/CURLOPT_FNMATCH_FUNCTION.html .. _CURLOPT_HSTSREADFUNCTION: https://curl.se/libcurl/c/CURLOPT_HSTSREADFUNCTION.html .. _CURLOPT_HSTSWRITEFUNCTION: https://curl.se/libcurl/c/CURLOPT_HSTSWRITEFUNCTION.html .. _ws_callback.py example: https://github.com/pycurl/pycurl/blob/master/examples/ws_callback.py