Develop Reference

Flask Form Action is not referring to the variable

I have a form and am passing the variable as below using Jinja template
<form action = "/user_data/{{period}}" method="POST">
It is not redirecting required page /user_data/Oct-2022
But while just using {{period}} for testing in html page, variable is returning the result as Oct-2022. Not sure why the same variable is not getting passed in the form action.
Variable is printing as below in html page,
{{period}}
But it is not printing in the form,
<form action = "/user_data/{{period}}" method="POST">
This is the route method,
#app.route("/user_listing/<period>", methods = ['POST', 'GET'])
def user_data(period):
....
....
return render_template('user_data.html', period=period)

First we imported the Flask class. An instance of this class will be our WSGI application.
Next we create an instance of this class. The first argument is the name of the application’s module or package. If you are using a single module (as in this example), you should use name because depending on if it’s started as application or imported as module the name will be different ('main' versus the actual import name). This is needed so that Flask knows where to look for templates, static files, and so on. For more information have a look at the Flask documentation.
We then use the route() decorator to tell Flask what URL should trigger our function.
The function is given a name which is also used to generate URLs for that particular function, and returns the message we want to display in the user’s browser.

Python Flask Jinja Dynamic routing

On the html page
{{ item.filename }}
On the flask routing code :
#app.route("/<username>/<filename>")
def downloadimage(username, filename):
However, this isn't routing the routing method.
What's the issue here ?

You can use the url_for method here.
Use it like this:
{{ item.filename }}
Here, downloadimage is the name of the function added to the required URL, username and filename are the parameters that should be passed to the function.

How can I pass a client-side parameter to a server-side route without using forms?

I have a simple Flask web app. My index template has various ways of interacting with clients using javascript and HTML. I am also have a form that, upon submission, routes to another flask process and uses the request.form command to retrieve user-submitted data.
However, I want to do something a little different. I would like to initiate a Flask redirection upon javascript event but include a parameter, and not use form.
For example, my index.html file would display something like this after template rendering:
function startRedirect(parameter) {
window.location.pathname = '/myRedirect';
}
<input type="checkbox" id="sample" name="sample" onChange="startRedirect(parameter);">
And part of my Flask script would have:
#app.route('/myRedirect')
def myRedirectFunction():
# do something with the parameter here
return render_template('index.html')
I realize this can be done with using a form, but I am interested in accomplishing this task without having a form. I was thinking about somehow using request.args, but don't quite understand what to do.

You can use a dynamic route to capture a simple input and pass it to the route's function.
app.route('/myRedirect/<param>')
def myRedirectFunction(param='hello world'):
return render_template('index.html', param=param)
Using this route as a redirect, you can pass a single param (or multiple if you serialize them) that you can use to do something. From there, you can either display or you can redirect again to a common endpoint so the user does not see the param in the url.

There's no need for a form or an explicit redirect, just attach a route and some parameter to the dynamic route.
Let's say you have a model to list the departments in your company:
class Departments(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(100), unique=True)
Now you have a department selection page:
#app.route('/departments_home', methods=['GET'])
def departments_home():
departments = Departments.query.all()
return render_template('departments_home.html',
departments=departments)
On the frontend you might have a variety of selections, each giving a link to the same route but with a different department_id:
{% for department in departments %}
Click to go to {{ department.name }}
{% endfor %}
Now you just need another route to handle this, taking the variable department_id that was passed in the GET request:
#app.route('/load_department/<department_id>', methods=['GET'])
def load_department(department_id):
department = Departments.query.get(int(department_id))
department_data = # do stuff here with the specific department

Python flask 'generating urls'?

I'm pretty new to flask any web development in general. So I was wondering how you generate a link. as in, when somene registers on your website you create a link like site.com/leak1953 and that would be their profile.

For generating links there exists the function flask.url_for() which generates a URL given the endpoint with a method provided. You can use this function also in JINJA2 templates. To provide an external link use
{{ url_for('index.main', _external=True) }}
If you want to include parameters to the url just add them to the url_for parameters.
{{ url_for(show_user_profile, username='Klaus') }}

Variable Rules
To add variable parts to a URL you can mark these special sections as . Such a part is then passed as a keyword argument to your function. Optionally a converter can be used by specifying a rule with <converter:variable_name>.
#app.route('/user/<username>')
def show_user_profile(username):
# show the user profile for that user
return 'User %s' % username
#app.route('/post/<int:post_id>')
def show_post(post_id):
# show the post with the given id, the id is an integer
return 'Post %d' % post_id
source: http://flask.pocoo.org/docs/0.12/quickstart/#variable-rules

confusion in url and template in django

My url is :
1. http://localhost:8000/docs/[slug]
2. http://localhost:8000/docs/[slug]/login
1. url calls before number 2. url I want to send
the slug value to the function mapped by the url 2. In template
what should i wrote for form action event.

I agree, this is nearly incomprehensible, but I'm going to give it a go in terms of an answer.
In terms of calling sequence, there is none. A user might first visit url 2 or url 1. You have no way of guaranteeing which they will try to access first because they might directly input the url into their browser. The only thing you can do is set a variable in request.session's dict and test for it with your login url.
In terms of passing slug to another url, if you're having a url with this in it:
urls = ('',
url(r'docs/(?P<slug>\w+)', 'app.views.slug', name='slug-view'),
url(r'docs/(?P<slug>\w+)/login', 'app.views.slug_login', name='slug-login'),
#..
)
Then in your template you can do this:
<form action="{% url slug-login slugname %}" method="POST">
Your views.py would look something like this.
def slug(request, slug):
#
#
return render_to_response('templatename.html', {'slugname':slug}, context_instance=RequestContext(request))
def slug_login(request, slug):
# do something with slug.
This way, when you access the slug view, you pass into the template a variable called slugname, which the template uses with django's url library to resolve a specifically named url in urls.py with one named parameter, slug, which it will assign the value of slugname.
I suggest you try it.
I might also reccoment you read up on the django url dispatcher. Your use of regex without named parameters is acceptable but really not best practice. I'd also suggest django shortcuts (render_to_response) as a quick way to pass variables into templates and the django template language itself.