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mrequests

An HTTP client module for MicroPython with an API similar to requests.

This is an evolution of the urequests module from micropython-lib with a few extensions and many fixes and convenience features.

Features & Limitations

Compatibility

Supports many MicroPython ports as well as CPython.

Features

• Supports SSL/TLS with server certificate validation (as far as supported by the ssl module of a given MicroPython port).
• Supports redirection with absolute and relative URLs (see below for details).
• Supports HTTP basic authentication (requires binascii module).
• Supports socket timeouts.
• Response headers can optionally be saved in the response object.
• Respects Content-length header in response.
• Supports responses with chunked transfer encoding.
• Response objects have a readinto method to store the response body to a given buffer (or memoryview) in chunks of maximum len(buffer) size.
• Response objects have save and saveto methods to save the response body to a file (given by filename resp. file object), reading the response data and writing the file in small chunks.
• The Response class for response objects can be substituted by a custom response class (usually defined by subclassing Response).

Limitations

• mrequests.request is a synchroneous, blocking function.

• The code is not interrupt save and a fair amount of memory allocation is happening in the process of handling a request.

• URL parsing does not cover all corner cases (see test_urlparse for details).

• URLs with authentication credentials in the host part (e.g. http://user:secret@myhost/) are not supported. Pass authentication credentials separately via the auth argument instead.

• SSL/TLS support on the MicroPython unix, stm32 and esp8266 ports is limited. In particular, their ssl module does not support all encryption schemes commonly in use by popular servers, meaning that trying to connect to them via HTTPS will fail with various cryptic error messages.

  On the esp8266 port no TLS server certificate validation is performed.

• Request and JSON data may be passed in as bytes or strings and the request data will be encoded to bytes, if necessary, using the encoding given with the encoding parameter. But be aware that encodings other than utf-8 are not supported by most (any?) MicroPython implementations.

• Custom headers may be passed as a dictionary with bytes keys and values and keys and values must contain only ASCII chars. If you need header values to use non-ASCII chars, you need to encode them according to RFC 8187.

  The header dictionary may contain also string keys and values, but:

  • Using MicroPython, it causes Warning: Comparison between bytes and str to be printed to the standard error output when calling request.
  • It causes additional memory allocations.
  • The "Host" header (if present) must always use b"Host" as the header dictionary key, i.e. it must be of type bytes and use this exact capitalization (unless the headers dictionary uses an implementation with case-insensitive key lookup).

• The URL and specifically any query string parameters it contains will not be URL-encoded, and it may contain only ASCII chars. Make sure you encode the query string part of the URL with urlencode.quote before passing it, if necessary.

• When encoding str instances via urlencode.urlencode or urlencode.quote, the encoding and errors arguments are currently ignored by MicroPython and it behaves as if their values were "utf-8" resp. "ignore".

• In responses using "chunked" transfer-encoding, chunk extensions and trailers are ignored.

Redirection Support

• Can follow redirects for response status codes 301, 302, 303, 307 and 308.
• The HTTP method is changed to GET for redirects, unless the original method was HEAD or the status code is 307 or 308.
• For status code 303, if the method of the request resulting in a redirection (which may have been the result of a previous redirection) is GET, the redirection is not followed, since the Location header is supposed to indicate a non-HTTP resource then.
• Redirects are allowed to change the protocol from http to https, but redirects changing from https to http will not be followed.
• The request function has an additional keyword argument max_redirects, defaulting to 1, which controls how many levels of redirections are followed. If this is exceeded, the function raises a ValueError.
• The code does not check for infinite redirection cycles. It is advised to keep max_redirects to a low number instead.

Installation

While there are multiple ways to install the library from your PC's command line, three different installation methods are provided via different scripts:

• install_mpremote.sh(Bash script using mpremote binary)
• install.sh (Bash script using rshell binary, legacy)
• install.py (Python script using mpremote as a library)

install_mpremote.sh

The following should be installed and in your shell's PATH:

• mpy-cross
• mpremote

Run the command:

./install_mpremote.sh

This will compile the Python modules with mpy-cross and copy the resulting .mpy files to the board's flash using the mpremote command.

install.sh

The following should be installed and in your shell's PATH:

• mpy-cross
• rshell

For boards with the stm32 port run:

DESTDIR=/flash ./install.sh

For boards with the esp8266 or esp32 port run:

DESTDIR=/pyboard PORT=/dev/ttyUSB0 BAUD=115200 ./install.sh

This will compile the Python modules with mpy-cross and copy the resulting .mpy files to the board's flash using the rshell comamnd.

install.py

The following should be installed and in your shell's PATH:

• mpy-cross

Also, mpremote should be available on your PYTHONPATH, e.g. installed via pip:

python -m pip install mpremote

Then simply run install.py:

./install.py

This will compile the Python modules with mpy-cross and copy the resulting .mpy files to the board's flash using the mpremote library. Run install.py -h to review installation options.

Manual installation

For the unix port, just copy the mrequest directory with all files in it to a directory, which is in sys.path, e.g. ~/.micropython/lib, or set the MICROPYPATH environment variable to a colon-separated list of directories including the one to which you copied the package directory.

Note: the mrequests/mrequests.py module has no dependencies besides modules usually already built in to the MicroPython firmware on all ports (as of version >= 1.15) and can be installed and used on its own if flash storage space or available RAM is scarce. The other modules in the mrequests package provide support for specific tasks like, for example, sending form-encoded request parameters or data or parsing url-encoded strings (see the scripts in the examples directory for examples of their use).

Examples

Below are some basic usage examples of the mrequests module. More examples for special tasks can be found in the scripts in the examples directory. Some of these examples require extra modules from micropython-lib. To install these requirements to a MicroPython board you can use mpremote:

mpremote mip install collections-defaultdict

Simple GET request with JSON response

>>> import mrequests as requests
>>> r = requests.get("http://httpbin.org/get",
                     headers={"Accept": "application/json"})
>>> print(r)
<Response object at 7f6f91631be0>
>>> print(r.content)
b'{\n  "args": {}, \n  "headers": {\n    "Accept": "application/json", \n
"Host": "httpbin.org", \n    "X-Amzn-Trace-Id": "Root=1-[redacted]"\n  }, \n
"origin": "[redacted]", \n  "url": "http://httpbin.org/get"\n}\n'
>>> print(r.text)
{
  "args": {},
  "headers": {
    "Accept": "application/json",
    "Host": "httpbin.org",
    "X-Amzn-Trace-Id": "Root=1-[redacted]"
  },
  "origin": "[redacted]",
  "url": "http://httpbin.org/get"
}

>>> print(r.json())
{'url': 'http://httpbin.org/get', 'headers': {'X-Amzn-Trace-Id':
'Root=1-[redacted]', 'Host': 'httpbin.org', 'Accept': 'application/json'},
'args': {}, 'origin': '[redacted]'}
>>> r.close()

It is mandatory to close response objects as soon as you finished working with them. On MicroPython platforms without full-fledged OS, not doing so may lead to resource leaks and malfunction.

HTTP Basic Auth

>>> import mrequests as requests
>>> user = "joedoe"
>>> password = "simsalabim"
>>> url = "http://httpbin.org/basic-auth/%s/%s" % (user, password)
>>> r = requests.get(url, auth=(user, password))
>>> print(r.text)
{
  "authenticated": true,
  "user": "joedoe"
}
>>> r.close()

Reference

The main function provided by mrequests is request, which takes an HTTP method and a URL as positional arguments and several optional keyword arguments and returns a Response object:

request(method, url, data=None, json=None, headers={}, auth=None,
        encoding=None, response_class=Response, save_headers=False,
        max_redirects=1, timeout=None, ssl_context=None)

Parameters:

method (str) - the HTTP request method as a string in all-caps.

url (str) - the URL of the request as a string. This must be an absolute URL, including the protocol (only http:// and https:// are supported) and a host name or IP address. The server name may be suffixed with a port number, separated by a colon. The default port is 80 for http URLs and 443 for https.

Authentication credentials in the host part are not supported (see the auth parameter below).

The URL may contain only ASCII chars. The caller is responsible for encoding any non-ASCII chars in the path or the query string (for example with urlencode.quote) or encoding IDN host names if necessary.

data (bytes, str) - the request body data as bytes or str instance. If given as a string, it will be converted to bytes using the encoding given with the encoding parameter (requiring additional memory to allocate the new bytes object). The caller is responsible for formatting the request data according to the content type specified in the request headers.

json (obj) - an object, which will be encoded as JSON and sent as the request body data. Also adds a Content-Type header with the value application/json. This overwrites data passed with the data parameter and allocates memory for the request data. To avoid allocation, pass a JSON-encoded byte string with the data parameter instead.

headers (dict) - a dictionary of additional request headers to sent. Keys and values should be bytes instances and may contain only ASCII chars. They may be str instances, but see "Limitations". str keys and values will be converted to bytes using ASCII encoding, which causes memory allocation.

A Content-Length header will always be added, using the length of the request data as the value. If no b"Host" key is present in the header dictionary, the Host header value will be generated based on the host name from the URL.

auth (tuple) - HTTP basic authentication credentials given as a (user, password) tuple of bytes objects or a callable, returning such a tuple. Some MicroPython versions may also accept str instances as the tuple elements but may issue a warning message. This will overwrite Authorization headers passed in with the headers parameter.

encoding (str) - the encoding of the request body data, if the the data is passed in as a str instance with the data or json parameters. Defauts to utf-8.

response_class (obj) - the class to use for the returned response objects. Defaults to mrequests.Response. Custom response classes should sub-class mrequests.Response and must take the same constructor arguments.

save_headers (bool) - a boolean, which is passed to the constructor of the response class instance, which determines whether it keeps a reference to the response headers in the instance. This is set to False by default to save memory. If set to True, the default response class will make the reponse header lines available via its headers instance attribute as a list of unparsed bytes objects.

max_redirects (int) - the maximum number of valid redirections to follow. Defaults to 1. If too many redirections are encountered, a ValueError is raised.

timeout (float) - sets the timeout for the connection socket as a non-negative float in seconds. Defaults to None, which blocks indefinitely. If a non-zero value is given, connection attempts or socket read/write operations will raise OSError if the timeout period value has elapsed before the operation has completed. If zero is given, the socket is put in non-blocking mode.

ssl_context (ssl.SSLContext) - pass a custom ssl.SSLContext instance to configure TLS encryption and certificate handling. If performing an HTTPS request and no SSL context is passed, a default one is created, which allows an encrypted connection, but does not require the server to present a valid certificate. If the MicroPython port has proper SSL support, it is strongly recommended to pass your own SSL context instance, which has its verify_mode attribute set to ssl.CERT_REQUIRED and the required certificates loaded. See the documentation of the ssl module for details.

Several convenience wrappers for creating request using common HTTP methods are available:

head(url, **kw)

get(url, **kw)

post(url, **kw)

put(url, **kw)

patch(url, **kw)

delete(url, **kw)

The url and all keyword arguments are simply passed to request.

Authors

mrequests is based on urequests, written by Paul Sokolovsky and part of micropython-lib and licensed under the MIT license. It was further developed and is maintained by Christopher Arndt.

License

mrequests is distributed under the terms of the MIT license and is free and Open Source software.

Please see the file LICENSE for details.