Flask download pdf

Application Development. IT Management. Project Management. Resources Blog Articles. Menu Help Create Join Login. Home Browse Development Frameworks Flask. Flask The Python micro framework for building web applications. SourceForge is not affiliated with Flask.

Add a Review. Get project updates , sponsored content from our select partners, and more. Create the below app. This file should be created under the project root directory. Notice how I create flask instance. Next I will create main. In the above source code, the root path or endpoint will simply render the UI.

This UI contains only one link for downloading a file from the server. Clicking on the link will ask user to save the file in a chosen location. The file type could be anything. As you see I have tested with four types of files.

What if the image is in-memory. The following worked for me for Python 3. BytesIO img. Hafizur Rahman Hafizur Rahman 1, 17 17 silver badges 28 28 bronze badges. Using this code on the server side, how I can I decode it in javascript? Encode the string as ascii then decode the bytes as base 64 and save it as an image?

Did you try: 1. Hello, is there a way you could update to reflect showing the js part? The conversion can be shown in the form of an example image that was read and converted to base64 format and then back to original. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

Post as a guest Name. Email Required, but never shown. This is an extension to the cookie standard and probably not supported by all browsers. If you have set Flask. A session makes it possible to remember information from one request to another. The way Flask does this is by using a signed cookie.

To access the current session you can use the session object:. The session object works pretty much like an ordinary dict, with the difference that it keeps track of modifications.

True if the session is new, False otherwise. True if the session object detected a modification. Be advised that modifications on mutable structures are not picked up automatically, in that situation you have to explicitly set the attribute to True yourself. Here an example:. The default is 31 days. If set to False which is the default the session will be deleted when the user closes the browser.

The session interface provides a simple way to replace the session implementation that Flask is using. We recommend just subclassing a dict and adding that mixin:. The default NullSession class that is created will complain that the secret key was not set. To replace the session interface on an application all you have to do is to assign flask. Returns True if the session cookie should be httponly. Returns the path for which the cookie should be valid. Return 'Strict' or 'Lax' if the cookie should use the SameSite attribute.

Returns True if the cookie should be secure. A helper method that returns an expiration date for the session or None if the session is linked to the browser session. Creates a null session which acts as a replacement object if the real session support could not be loaded due to a configuration error.

This mainly aids the user experience because the job of the null session is to still support lookup without complaining but modifications are answered with a helpful error message of what failed. A flag that indicates if the session interface is pickle based. This can be used by Flask extensions to make a decision in regards to how to deal with the session object. This is still called during a request context so if you absolutely need access to the request you can do that.

Used by session backends to determine if a Set-Cookie header should be set for this session cookie for this response. If the session has been modified, the cookie is set.

The default session interface that stores sessions in signed cookies through the itsdangerous module. A python serializer for the payload.

The default is a compact JSON derived serializer with support for some extra Python types such as datetime objects or tuples. This session backend will set the modified and accessed attributes. It cannot reliably track whether a session is new vs. When data is changed, this is set to True. Only the session dictionary itself is tracked; if the session contains mutable data for example a nested dict then this must be set to True manually when modifying that data.

The session cookie will only be written to the response if this is True. Class used to generate nicer error messages if sessions are not available. Will still allow read-only access to the empty session but fail on setting. Some implementations can detect when session data is read or written and set this when that happens.

The mixin default is hard coded to True. Some implementations can detect changes to the session and set this when that happens. Works like a regular Werkzeug test client but has some knowledge about how Flask works to defer the cleanup of the request context stack to the end of a with body when used in a with statement. For general information about how to use this class refer to werkzeug.

Basic usage is outlined in the Testing Flask Applications chapter. This change was made for consistency with werkzeug. This will automatically close the application for you as well. When used in combination with a with statement this opens a session transaction. This can be used to modify the session that the test client uses. Once the with block is left the session is stored back. Invokes a CLI command in an isolated environment. See CliRunner. If the obj argument is not given, passes an instance of ScriptInfo that knows how to load the Flask app being tested.

To share data that is valid for one request only from one function to another, a global variable is not good enough because it would break in threaded environments. Flask provides you with a special object that ensures it is only valid for the active request and that will return different values for each request. In a nutshell: it does the right thing, like it does for request and session. A namespace object that can store data during an application context. This is an instance of Flask.

This is a good place to store resources during a request. During testing, you can use the Faking Resources and Context pattern to pre-configure such resources. Creating an app context automatically creates this object, which is made available as the g proxy. Get an attribute by name, or a default value. Like dict. Get and remove an attribute by name. Get the value of an attribute if it is present, otherwise set and return a default value. A proxy to the application handling the current request.

This is only available when an application context is pushed. This happens automatically during requests and CLI commands.

If you have code that wants to test if a request context is there or not this function can be used. For instance, you may want to take advantage of request information if the request object is available, but fail silently if it is unavailable. Alternatively you can also just test any of the context bound objects such as request or g for truthness:. A helper function that decorates a function to retain the current request context.

This is useful when working with greenlets. The moment the function is decorated a copy of the request context is created and then pushed when the function is called. The current session is also included in the copied request context. Variable arguments that are unknown to the target endpoint are appended to the generated URL as query arguments. If the value of a query argument is None , the whole pair is skipped.

In case blueprints are active you can shortcut references to the same blueprint by prefixing the local endpoint with a dot. For more information, head over to the Quickstart. An example:. Note that this is for building URLs outside the current application, and not for handling NotFound errors.

If a status code is given, it will be looked up in the list of exceptions and will raise that exception. Returns a response object a WSGI application that, if called, redirects the client to the target location.

Supported codes are , , , , , and Response class — a Response class to use when instantiating a response. The default is werkzeug. Response if unspecified. Sometimes it is necessary to set additional headers in a view.

Because views do not have to return response objects but can return a value that is converted into a response object by Flask itself, it becomes tricky to add headers to it.

This function can be called instead of using a return and you will get a response object which you can use to attach headers. This function accepts the very same arguments you can return from a view function. This for example creates a response with a error code:.

The other use case of this function is to force the return value of a view function into a response which is helpful with view decorators:. Executes a function after this request. This is useful to modify response objects. The function is passed the response object and has to return the same or a new one. This is more useful if a function other than the view function wants to modify a response. For instance think of a decorator that wants to add some headers without converting the return value into a response object.

Sends the contents of a file to the client. This will use the most efficient method available and configured. This however requires support of the underlying webserver for X-Sendfile.

By default it will try to guess the mimetype for you, but you can also explicitly provide one. For extra security you probably want to send certain files as attachment HTML for instance. ETags will also be attached automatically if a filename is provided.

This will allow the request to be answered with partial content response. Pass a filename if you are able to, otherwise attach an etag yourself. This functionality will be removed in Flask 1. The default behavior is now to attach etags. Alternatively a file object might be provided in which case X-Sendfile might not work and fall back to the traditional method. If a file path is given, auto detection happens as fallback, otherwise an error will be raised. If a file was passed, this overrides its mtime.

This is a secure way to quickly expose static files from an upload folder or something similar. It is strongly recommended to activate either X-Sendfile support in your webserver or if no authentication happens to tell the webserver to serve files for the given path on its own without calling into the web application for improved performance.

NotFound if one or more passed paths fall out of its boundaries. Escape a string. Calls escape and ensures that for subclasses the correct type is returned. Convert escaped markup back into a text string. This replaces HTML entities with the characters they represent. Flashes a message to the next request. The following values are recommended: 'message' for any kind of message, 'error' for errors, 'info' for information messages and 'warning' for warnings.

However any kind of string can be used as category. Pulls all flashed messages from the session and returns them. Further calls in the same request to the function will return the same messages. This allows rendering categories in separate html blocks. See Message Flashing for examples. Flask uses simplejson for the JSON implementation. Since simplejson is provided by both the standard library as well as extension, Flask will try simplejson first and then fall back to the stdlib json module.

For usage examples, read the json documentation in the standard library. Note that in versions of Flask prior to Flask 0. In Flask 0. By default sorting is enabled and outside of the app context sorting is turned on. This function wraps dumps to add a few enhancements that make life easier. For convenience, it also converts multiple arguments into an array or multiple keyword arguments into a dict. This means that both jsonify 1,2,3 and jsonify [1,2,3] serialize to [1,2,3].

For clarity, the JSON serialization behavior has the following differences from dumps :. Single argument: Passed straight through to dumps.

Multiple arguments: Converted to an array before being passed to dumps. Multiple keyword arguments: Converted to a dict before being passed to dumps. This introduces a security risk in ancient browsers. Compressed not pretty formatting currently means no indents and no spaces after separators. Serialize obj to a JSON-formatted string. Takes the same arguments as the built-in json. If the simplejson package is installed, it is preferred. Like dumps but writes into a file object.

Deserialize an object from a JSON-formatted string s. Like loads but reads from a file object. This one extends the default encoder by also supporting datetime , UUID , dataclasses , and Markup objects. This is the same as the HTTP date format. In order to support more data types, override the default method. Implement this method in a subclass such that it returns a serializable object for o , or calls the base implementation to raise a TypeError.

The default JSON decoder. This one does not change the behavior from the default simplejson decoder. Consult the json documentation for more information. This decoder is not only used for the load functions of this module but also Request. A compact representation for lossless serialization of non-standard JSON types. SecureCookieSessionInterface uses this to serialize the session data, but it may be useful in other places.

It can be extended to support other types. Serializer that uses a tag system to compactly represent objects that are not JSON types.

Passed as the intermediate serializer to itsdangerous. Tag classes to bind when creating the serializer. Other tags can be added later using register. Will be instantiated with this serializer instance. If false default , a KeyError is raised. Useful when the new tag is a special case of an existing tag. If None default , the tag is appended to the end of the order. KeyError — if the tag key is already registered and force is not true.

The tag to mark the serialized object with. If None , this tag is only used as an intermediate step during tagging. The session serializer processes dicts first, so insert the new tag at the front of the order since OrderedDict must be processed before dict.