Urllib error httperror http error 403 forbidden python



[Fixed] urllib.error.httperror: http error 403: forbidden

The urllib module can be used to make an HTTP request from a site, unlike the requests library, which is a built-in library. This reduces dependencies. In the following article, we will discuss why urllib.error.httperror: http error 403: forbidden occurs and how to resolve it.

What is a 403 error?

The 403 error pops up when a user tries to access a forbidden page or, in other words, the page they aren’t supposed to access. 403 is the HTTP status code that the webserver uses to denote the kind of problem that has occurred on the user or the server end . For instance, 200 is the status code for – ‘everything has worked as expected, no errors’. You can go through the other HTTP status code from here.

Why urllib.error.httperror: http error 403: forbidden occurs?

ModSecurity is a module that protects websites from foreign attacks. It checks whether the requests are being made from a user or from an automated bot. It blocks requests from known spider/bot agents who are trying to scrape the site. Since the urllib library uses something like python urllib/3.3.0 hence, it is easily detected as non-human and therefore gets blocked by mod security.

ModSecurity blocks the request and returns an HTTP error 403: forbidden error if the request was made without a valid user agent. A user-agent is a header that permits a specific string which in turn allows network protocol peers to identify the following:

  • The Operating System, for instance, Windows, Linux, or macOS.
  • Websserver’s browser

Moreover, the browser sends the user agent to each and every website that you get connected to. The user-Agent field is included in the HTTP header when the browser gets connected to a website. The header field data differs for each browser.

Why do sites use security that sends 403 responses?

According to a survey, more than 50% of internet traffic comes from automated sources. Automated sources can be scrapers or bots. Therefore it gets necessary to prevent these attacks. Moreover, scrapers tend to send multiple requests, and sites have some rate limits. The rate limit dictates how many requests a user can make. If the user(here scraper) exceeds it, it gets some kind of error, for instance, urllib.error.httperror: http error 403: forbidden.

Resolving urllib.error.httperror: http error 403: forbidden?

This error is caused due to mod security detecting the scraping bot of the urllib and blocking it. Therefore, in order to resolve it, we have to include user-agent/s in our scraper. This will ensure that we can safely scrape the website without getting blocked and running across an error. Let’s take a look at two ways to avoid urllib.error.httperror: http error 403: forbidden.

Method 1: using user-agent

  • In the code above, we have added a new parameter called headers which has a user-agent Mozilla/5.0. Details about the user’s device, OS, and browser are given by the webserver by the user-agent string. This prevents the bot from being blocked by the site.
  • For instance, the user agent string gives information to the server that you are using Brace browser and Linux OS on your computer. Thereafter, the server accordingly sends the information.

Using the user-agent, the error gets resolved.

Method 2: using Session object

There are times when even using user-agent won’t prevent the urllib.error.httperror: http error 403: forbidden. Then we can use the Session object of the request module. For instance:

The site could be using cookies as a defense mechanism against scraping. It’s possible the site is setting and requesting cookies to be echoed back as a defense against scraping, which might be against its policy.

The Session object is compatible with cookies.

Using Session object to resolve urllib.error

Catching urllib.error.httperror

urllib.error.httperror can be caught using the try-except method. Try-except block can capture any exception, which can be hard to debug. For instance, it can capture exceptions like SystemExit and KeyboardInterupt. Let’s see how can we do this, for instance:

You can try the following steps in order to resolve the 403 error in the browser try refreshing the page, rechecking the URL, clearing the browser cookies, check your user credentials.

Scrapers often don’t use headers while requesting information. This results in their detection by the mod security. Hence, scraping modules often get 403 errors.

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Python urllib.error.httperror: http error 403: forbidden

The urllib.error.httperror: http error 403: forbidden occurs when you try to scrap a webpage using urllib.request module and the mod_security blocks the request. There are several reasons why you get this error. Let’s take a look at each of the use cases in detail.

How to fix urllib.error.httperror: http error 403: forbidden?

Usually, the websites are protected with App Gateway, WAF rules, etc., which monitor whether the requests are from the actual users or triggered through the automated bot system. The mod_security or the WAF rule will block these requests treating them as spider/bot requests. These security features are the most standard ones to prevent DDOS attacks on the server.

Now coming back to the error when you make a request to any site using urllib.request basically, you will not set any user-agents and headers and by default the urllib sets something like python urllib/3.3.0, which is easily detected by the mod_security.

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The mod_security is usually configured in such a way that if any requests happen without a valid user-agent header(browser user-agent), the mod_security will block the request and return the urllib.error.httperror: http error 403: forbidden

Example of 403 forbidden error

Output

The easy way to resolve the error is by passing a valid user-agent as a header parameter, as shown below.

Alternatively, you can even set a timeout if you are not getting the response from the website. Python will raise a socket exception if the website doesn’t respond within the mentioned timeout period.

In some cases, like getting a real-time bitcoin or stock market value, you will send requests every second, and the servers can block if there are too many requests coming from the same IP address and throws 403 security error.

If you get this error because of too many requests, consider adding delay between each request to resolve the error.

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HOWTO Fetch Internet Resources Using The urllib Package¶

There is a French translation of an earlier revision of this HOWTO, available at urllib2 — Le Manuel manquant.

Introduction¶

You may also find useful the following article on fetching web resources with Python:

A tutorial on Basic Authentication, with examples in Python.

urllib.request is a Python module for fetching URLs (Uniform Resource Locators). It offers a very simple interface, in the form of the urlopen function. This is capable of fetching URLs using a variety of different protocols. It also offers a slightly more complex interface for handling common situations — like basic authentication, cookies, proxies and so on. These are provided by objects called handlers and openers.

urllib.request supports fetching URLs for many “URL schemes” (identified by the string before the «:» in URL — for example «ftp» is the URL scheme of «ftp://python.org/» ) using their associated network protocols (e.g. FTP, HTTP). This tutorial focuses on the most common case, HTTP.

For straightforward situations urlopen is very easy to use. But as soon as you encounter errors or non-trivial cases when opening HTTP URLs, you will need some understanding of the HyperText Transfer Protocol. The most comprehensive and authoritative reference to HTTP is RFC 2616. This is a technical document and not intended to be easy to read. This HOWTO aims to illustrate using urllib, with enough detail about HTTP to help you through. It is not intended to replace the urllib.request docs, but is supplementary to them.

Fetching URLs¶

The simplest way to use urllib.request is as follows:

If you wish to retrieve a resource via URL and store it in a temporary location, you can do so via the shutil.copyfileobj() and tempfile.NamedTemporaryFile() functions:

Many uses of urllib will be that simple (note that instead of an ‘http:’ URL we could have used a URL starting with ‘ftp:’, ‘file:’, etc.). However, it’s the purpose of this tutorial to explain the more complicated cases, concentrating on HTTP.

HTTP is based on requests and responses — the client makes requests and servers send responses. urllib.request mirrors this with a Request object which represents the HTTP request you are making. In its simplest form you create a Request object that specifies the URL you want to fetch. Calling urlopen with this Request object returns a response object for the URL requested. This response is a file-like object, which means you can for example call .read() on the response:

Note that urllib.request makes use of the same Request interface to handle all URL schemes. For example, you can make an FTP request like so:

In the case of HTTP, there are two extra things that Request objects allow you to do: First, you can pass data to be sent to the server. Second, you can pass extra information (“metadata”) about the data or about the request itself, to the server — this information is sent as HTTP “headers”. Let’s look at each of these in turn.

Data¶

Sometimes you want to send data to a URL (often the URL will refer to a CGI (Common Gateway Interface) script or other web application). With HTTP, this is often done using what’s known as a POST request. This is often what your browser does when you submit a HTML form that you filled in on the web. Not all POSTs have to come from forms: you can use a POST to transmit arbitrary data to your own application. In the common case of HTML forms, the data needs to be encoded in a standard way, and then passed to the Request object as the data argument. The encoding is done using a function from the urllib.parse library.

Note that other encodings are sometimes required (e.g. for file upload from HTML forms — see HTML Specification, Form Submission for more details).

If you do not pass the data argument, urllib uses a GET request. One way in which GET and POST requests differ is that POST requests often have “side-effects”: they change the state of the system in some way (for example by placing an order with the website for a hundredweight of tinned spam to be delivered to your door). Though the HTTP standard makes it clear that POSTs are intended to always cause side-effects, and GET requests never to cause side-effects, nothing prevents a GET request from having side-effects, nor a POST requests from having no side-effects. Data can also be passed in an HTTP GET request by encoding it in the URL itself.

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This is done as follows:

Notice that the full URL is created by adding a ? to the URL, followed by the encoded values.

Headers¶

We’ll discuss here one particular HTTP header, to illustrate how to add headers to your HTTP request.

Some websites 1 dislike being browsed by programs, or send different versions to different browsers 2. By default urllib identifies itself as Python-urllib/x.y (where x and y are the major and minor version numbers of the Python release, e.g. Python-urllib/2.5 ), which may confuse the site, or just plain not work. The way a browser identifies itself is through the User-Agent header 3. When you create a Request object you can pass a dictionary of headers in. The following example makes the same request as above, but identifies itself as a version of Internet Explorer 4.

The response also has two useful methods. See the section on info and geturl which comes after we have a look at what happens when things go wrong.

Handling Exceptions¶

urlopen raises URLError when it cannot handle a response (though as usual with Python APIs, built-in exceptions such as ValueError , TypeError etc. may also be raised).

HTTPError is the subclass of URLError raised in the specific case of HTTP URLs.

The exception classes are exported from the urllib.error module.

URLError¶

Often, URLError is raised because there is no network connection (no route to the specified server), or the specified server doesn’t exist. In this case, the exception raised will have a ‘reason’ attribute, which is a tuple containing an error code and a text error message.

HTTPError¶

Every HTTP response from the server contains a numeric “status code”. Sometimes the status code indicates that the server is unable to fulfil the request. The default handlers will handle some of these responses for you (for example, if the response is a “redirection” that requests the client fetch the document from a different URL, urllib will handle that for you). For those it can’t handle, urlopen will raise an HTTPError . Typical errors include ‘404’ (page not found), ‘403’ (request forbidden), and ‘401’ (authentication required).

See section 10 of RFC 2616 for a reference on all the HTTP error codes.

The HTTPError instance raised will have an integer ‘code’ attribute, which corresponds to the error sent by the server.

Error Codes¶

Because the default handlers handle redirects (codes in the 300 range), and codes in the 100–299 range indicate success, you will usually only see error codes in the 400–599 range.

http.server.BaseHTTPRequestHandler.responses is a useful dictionary of response codes in that shows all the response codes used by RFC 2616. The dictionary is reproduced here for convenience

When an error is raised the server responds by returning an HTTP error code and an error page. You can use the HTTPError instance as a response on the page returned. This means that as well as the code attribute, it also has read, geturl, and info, methods as returned by the urllib.response module:

Wrapping it Up¶

So if you want to be prepared for HTTPError or URLError there are two basic approaches. I prefer the second approach.

Number 1В¶

The except HTTPError must come first, otherwise except URLError will also catch an HTTPError .

Number 2В¶

info and geturl¶

The response returned by urlopen (or the HTTPError instance) has two useful methods info() and geturl() and is defined in the module urllib.response ..

geturl — this returns the real URL of the page fetched. This is useful because urlopen (or the opener object used) may have followed a redirect. The URL of the page fetched may not be the same as the URL requested.

info — this returns a dictionary-like object that describes the page fetched, particularly the headers sent by the server. It is currently an http.client.HTTPMessage instance.

Typical headers include ‘Content-length’, ‘Content-type’, and so on. See the Quick Reference to HTTP Headers for a useful listing of HTTP headers with brief explanations of their meaning and use.

Openers and Handlers¶

When you fetch a URL you use an opener (an instance of the perhaps confusingly named urllib.request.OpenerDirector ). Normally we have been using the default opener — via urlopen — but you can create custom openers. Openers use handlers. All the “heavy lifting” is done by the handlers. Each handler knows how to open URLs for a particular URL scheme (http, ftp, etc.), or how to handle an aspect of URL opening, for example HTTP redirections or HTTP cookies.

You will want to create openers if you want to fetch URLs with specific handlers installed, for example to get an opener that handles cookies, or to get an opener that does not handle redirections.

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To create an opener, instantiate an OpenerDirector , and then call .add_handler(some_handler_instance) repeatedly.

Alternatively, you can use build_opener , which is a convenience function for creating opener objects with a single function call. build_opener adds several handlers by default, but provides a quick way to add more and/or override the default handlers.

Other sorts of handlers you might want to can handle proxies, authentication, and other common but slightly specialised situations.

install_opener can be used to make an opener object the (global) default opener. This means that calls to urlopen will use the opener you have installed.

Opener objects have an open method, which can be called directly to fetch urls in the same way as the urlopen function: there’s no need to call install_opener , except as a convenience.

Basic Authentication¶

To illustrate creating and installing a handler we will use the HTTPBasicAuthHandler . For a more detailed discussion of this subject – including an explanation of how Basic Authentication works — see the Basic Authentication Tutorial.

When authentication is required, the server sends a header (as well as the 401 error code) requesting authentication. This specifies the authentication scheme and a ‘realm’. The header looks like: WWW-Authenticate: SCHEME realm=»REALM» .

The client should then retry the request with the appropriate name and password for the realm included as a header in the request. This is ‘basic authentication’. In order to simplify this process we can create an instance of HTTPBasicAuthHandler and an opener to use this handler.

The HTTPBasicAuthHandler uses an object called a password manager to handle the mapping of URLs and realms to passwords and usernames. If you know what the realm is (from the authentication header sent by the server), then you can use a HTTPPasswordMgr . Frequently one doesn’t care what the realm is. In that case, it is convenient to use HTTPPasswordMgrWithDefaultRealm . This allows you to specify a default username and password for a URL. This will be supplied in the absence of you providing an alternative combination for a specific realm. We indicate this by providing None as the realm argument to the add_password method.

The top-level URL is the first URL that requires authentication. URLs “deeper” than the URL you pass to .add_password() will also match.

In the above example we only supplied our HTTPBasicAuthHandler to build_opener . By default openers have the handlers for normal situations – ProxyHandler (if a proxy setting such as an http_proxy environment variable is set), UnknownHandler , HTTPHandler , HTTPDefaultErrorHandler , HTTPRedirectHandler , FTPHandler , FileHandler , DataHandler , HTTPErrorProcessor .

top_level_url is in fact either a full URL (including the ‘http:’ scheme component and the hostname and optionally the port number) e.g. «http://example.com/» or an “authority” (i.e. the hostname, optionally including the port number) e.g. «example.com» or «example.com:8080» (the latter example includes a port number). The authority, if present, must NOT contain the “userinfo” component — for example «joe:password@example.com» is not correct.

Proxies¶

urllib will auto-detect your proxy settings and use those. This is through the ProxyHandler , which is part of the normal handler chain when a proxy setting is detected. Normally that’s a good thing, but there are occasions when it may not be helpful 5. One way to do this is to setup our own ProxyHandler , with no proxies defined. This is done using similar steps to setting up a Basic Authentication handler:

Currently urllib.request does not support fetching of https locations through a proxy. However, this can be enabled by extending urllib.request as shown in the recipe 6.

HTTP_PROXY will be ignored if a variable REQUEST_METHOD is set; see the documentation on getproxies() .

Sockets and Layers¶

The Python support for fetching resources from the web is layered. urllib uses the http.client library, which in turn uses the socket library.

As of Python 2.3 you can specify how long a socket should wait for a response before timing out. This can be useful in applications which have to fetch web pages. By default the socket module has no timeout and can hang. Currently, the socket timeout is not exposed at the http.client or urllib.request levels. However, you can set the default timeout globally for all sockets using

Footnotes¶

This document was reviewed and revised by John Lee.

Google for example.

Browser sniffing is a very bad practice for website design — building sites using web standards is much more sensible. Unfortunately a lot of sites still send different versions to different browsers.

The user agent for MSIE 6 is ‘Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)’

For details of more HTTP request headers, see Quick Reference to HTTP Headers.

In my case I have to use a proxy to access the internet at work. If you attempt to fetch localhost URLs through this proxy it blocks them. IE is set to use the proxy, which urllib picks up on. In order to test scripts with a localhost server, I have to prevent urllib from using the proxy.

urllib opener for SSL proxy (CONNECT method): ASPN Cookbook Recipe.

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