A user agent is a computer program representing a person, for example, a browser in a Web context.
Besides a browser, a user agent could be a bot scraping webpages, a download manager, or another app accessing the Web. Along with each request they make to the server, browsers include a self-identifying User-Agent HTTP header called a user agent (UA) string. This string often identifies the browser, its version number, and its host operating system.
Spam bots, download managers, and some browsers often send a fake UA string to announce themselves as a different client. This is known as user agent spoofing.
A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".
Web servers use this data to assess the capabilities of your computer, optimizing a page’s performance and display. Before we look into rotating user agents, let’s see how to fake or spoof an user agent in a request.
Disclaimer: Any code provided in our tutorials is for illustration and learning purposes only. We are not responsible for how it is used and assume no liability for any detrimental usage of the source code.
The tutorials only help illustrate the technique of programming web scrapers for popular internet websites. We are not obligated to provide any support for the code, however, if you add your questions in the comments section, we may periodically address them.
But I think this approach is misguided as it may see your crawlers make thousands of requests from very rarely used user agents. Thankfully, the majority of system administrators completely ignore the intricacies of the scent ‘Accept’ headers and simply check if browsers are sending something plausible.
If you're not sure which to choose, learn more about installing packages. Accessing websites from a Python program is not very difficult, but using the requests' library makes it even fun.
If you run this program it will send the request as if it was Internet Explorer 2.0 and let the system administrator wonder if you are really stuck with such an old browser. If you have any comments or questions, feel free to post them on the source of this page in GitHub.
One aspect that affects all three of these specializations is the powerful benefits of APIs. Pulling in data, and connecting to external services, is an essential part of any language.
In this article, we'll look at the primary libraries for making HTTP requests, along with some common use cases that allow you to connect to an API in Python. It seems like a strange question, but given the large web presence of Node.js and Ruby, you may think that Python isn't good for making API calls.
In fact, Python has had a long and dedicated presence on the web, specifically with its Flask and Django libraries. Let's start with the most popular Python HTTP library used for making API calls.
The following examples will all assume that your project includes Requests. Often, an APIs documentation will require that you pass query parameters to a specific endpoint.
The response variable contains the data returned by the API in our examples. In addition to the body of the response, we can also access the status code with response.status_code, the headers with response.headers, and so on.
You can find a full list of properties and methods available on Response in the requests. Response documentation. The last common API call type we'll make is a full-featured POST, with authentication.
This will encode the payload as JSON, as well as automatically change the Content-Type header to application/Jason. When making asynchronous HTTP requests, you'll need to take advantage of some newer features in Python 3.
Used together with the Asuncion, we can use Giotto to make requests in an asynchronous way. To start, import both libraries, and define an asynchronous function.
Finally, we use the run method of Python's Asuncion to call the asynchronous function. If you haven't worked with asynchronous in Python before, this may look strange and complicated compared to the earlier examples.
The session uses the post method, and passes in headers and Jason dictionaries in addition to the URL. For additional features like file uploading and form data, take a look at Giotto's developer documentation.
While Requests is the most popular, you may find value in some of these additional libraries for more unique use cases. Currently, the library is in a beta state with a 1.0 expected min-summer 2020, but it is worth keeping an eye on as it matures.
Urllib3 : We should urllib3, if only because it is the underlying library that Requests and many others (including pip) are built on top of. With Python's power in data processing and recent resurgence, thanks in part of the ML and data science communities, it is a great option for interacting with APIs.
It is important to remember that even the most battle-tested and popular third-party APIs and services still suffer problems and outages. At Bearer, we're building tools to help manage these problems and better monitor your third-party APIs.
The Session object allows you to persist certain parameters across requests. It also persists cookies across all requests made from the Session instance, and will use urllib3 ’s.
A Session object has all the methods of the main Requests API. Sessions can also be used to provide default data to the request methods.
Any dictionaries that you pass to a request method will be merged with the session-level values that are set. This will make sure the session is closed as soon as the with block is exited, even if unhandled exceptions occurred.
In some cases you may wish to do some extra work to the body or headers (or anything else really) before sending a request. However, the above code will lose some advantages of having a Requests Session object.
When you are using the prepared request flow, keep in mind that it does not take into account the environment. This can cause problems if you are using environment variables to change the behavior of requests.
By default, SSL verification is enabled, and Requests will throw a Error if it’s unable to verify the certificate: I don’t have SSL setup on this domain, so it throws an exception.
You can pass verify the path to a CA_BUNDLE file or directory with certificates of trusted CAS: This list of trusted CAS can also be specified through the REQUESTS _CA_BUNDLE environment variable.
Note that when verify is set to False, requests will accept any TLS certificate presented by the server, and will ignore hostname mismatches and/or expired certificates, which will make your application vulnerable to man-in-the-middle (Mite) attacks. Setting verify to False may be useful during local development or testing.
This allows for users to update their trusted certificates without changing the version of Requests. When certify was not installed, this led to extremely out-of-date certificate bundles when using ancient versions of Requests.
For the sake of security we recommend upgrading certify frequently! By default, when you make a request, the body of the response is downloaded immediately.
Any requests that you make within a session will automatically reuse the appropriate connection! Note that connections are only released back to the pool for reuse once all body data has been read; be sure to either set stream to False or read the content property of the Response object.
To stream and upload, simply provide a file-like object for your body: This is because Requests may attempt to provide the Content-Length header for you, and if it does this value will be set to the number of bytes in the file.
In an ideal situation you’ll have set stream=True on the request, in which case you can iterate chunk-by-chunk by calling iter_content with a chunk_size parameter of None. This is because Requests may attempt to provide the Content-Length header for you, and if it does this value will be set to the number of bytes in the file.
Errors may occur if you open the file in text mode. If the callback function returns a value, it is assumed that it is to replace the data that was passed in.
Let’s print some request method arguments at runtime: Any hooks you add will then be called on every request made to the session.
A Session can have multiple hooks, which will be called in the order they are added. Let’s pretend that we have a web service that will only respond if the X-Pizza header is set to a password value.
Simply set stream to True and iterate over the response with : Calling this method multiple times causes some received data being lost.
In case you need to call it from multiple places, use the resulting iterator object instead: Storing sensitive username and password information in an environment variable or a version-controled file is a security risk and is highly discouraged.
Using the scheme socks5 causes the DNS resolution to happen on the client, rather than on the proxy server. This is in line with curl, which uses the scheme to decide whether to do the DNS resolution on the client or proxy.
Requests is intended to be compliant with all relevant specifications and RFCs where that compliance will not cause difficulties for users. Request provides access to almost the full range of HTTP verbs: GET, OPTIONS, HEAD, POST, PUT, PATCH and DELETE.
The following provides detailed examples of using these various verbs in Requests, using the GitHub API. HTTP GET is an idempotent method that returns a resource from a given URL.
As a result, it is the verb you ought to use when attempting to retrieve data from a web location. An example usage would be attempting to get information about a specific commit from GitHub.
We can take advantage of the Requests OPTIONS verb to see what kinds of HTTP methods are supported on the URL we just used. Turns out GitHub, like many API providers, don’t actually implement the OPTIONS method.
If GitHub had correctly implemented OPTIONS, however, they should return the allowed methods in the headers, e.g. OK, so let’s tell this Kenneth guy that we think this example should go in the quick start guide instead.
Request makes it easy to use many forms of authentication, including the very common Basic Auth. Happily, GitHub allows us to use another HTTP verb, PATCH, to edit this comment.
Now, just to torture this Kenneth guy, I’ve decided to let him sweat and not tell him that I’m working on this. Utilizing this, you can make use of any method verb that your server allows.
Transport Adapters provide a mechanism to define interaction methods for an HTTP service. This adapter provides the default Requests interaction with HTTP and HTTPS using the powerful urllib3 library.
Request enables users to create and use their own Transport Adapters that provide specific functionality. Once created, a Transport Adapter can be mounted to a Session object, along with an indication of which web services it should apply to.
The mount call registers a specific instance of a Transport Adapter to a prefix. Once mounted, any HTTP request made using that session whose URL starts with the given prefix will use the given Transport Adapter.
Many of the details of implementing a Transport Adapter are beyond the scope of this documentation, but take a look at the next example for a simple SSL use- case. The Requests team has made a specific choice to use whatever SSL version is default in the underlying library (urllib3).
With the default Transport Adapter in place, Requests does not provide any kind of non-blocking IO. If you are concerned about the use of blocking IO, there are lots of projects out there that combine Requests with one of Python ’s synchronicity frameworks.
By default, requests do not time out unless a timeout value is set explicitly. It’s a good practice to set connect timeouts to slightly larger than a multiple of 3, which is the default TCP packet retransmission window.
(Specifically, it’s the number of seconds that the client will wait between bytes sent from the server. If the remote server is very slow, you can tell Requests to wait forever for a response, by passing None as a timeout value and then retrieving a cup of coffee.