c# pdf to image: Extracting data from pdf forms to excel control application platform web page azure html web browser Flask14-part345

3. otherwise the original function is called and the return value is stored in the

cache for the timeout provided (by default 5 minutes).

Here the code:

from functools import t wraps

from flask import request

def cached(timeout=5 * 60, key=view/%s):

def decorator(f):

@wraps(f)

def decorated_function(*args, **kwargs):

cache_key = key % request.path

rv = cache.get(cache_key)

if rv is not None:

return rv

rv = f(*args, , **kwargs)

cache.set(cache_key, rv, timeout=timeout)

return rv

return decorated_function

return decorator

Notice that this assumes an instantiated cache object is available, see Caching for more

information.

18.12.3 Templating Decorator

Acommon pattern invented by the TurboGears guys a while back is a templating

decorator. The idea of that decorator is that you return a dictionary with the values

passed to the template from the view function and the template is automatically ren-

dered. With that, the following three examples do exactly the same:

@app.route(/)

def index():

return render_template(index.html, value=42)

@app.route(/)

@templated(index.html)

def index():

return dict(value=42)

@app.route(/)

@templated()

def index():

return dict(value=42)

As you can see, if no template name is provided it will use the endpoint of the URL

map with dots converted to slashes + ’.html’. Otherwise the provided template name

is used. When the decorated function returns, the dictionary returned is passed to the

template rendering function. If None is returned, an empty dictionary is assumed, if

131

Extracting data from pdf forms to excel - extract form data from PDF in C#.net, ASP.NET, MVC, Ajax, WPF

Help to Read and Extract Field Data from PDF with a Convenient C# Solution

saving pdf forms in acrobat reader; how to save fillable pdf form in reader

Extracting data from pdf forms to excel - VB.NET PDF Form Data Read library: extract form data from PDF in vb.net, ASP.NET, MVC, Ajax, WPF

Convenient VB.NET Solution to Read and Extract Field Data from PDF

how to make pdf editable form reader; pdf data extractor

something else than a dictionary is returned we return it fromthe function unchanged.

That way you can still use the redirect function or return simple strings.

Here the code for that decorator:

from functools import t wraps

from flask import request

def templated(template=None):

def decorator(f):

@wraps(f)

def decorated_function(*args, **kwargs):

template_name = template

if template_name is s None:

template_name = request.endpoint \

.replace(., /) + + .html

ctx = f(*args, , **kwargs)

if ctx is None:

ctx = {}

elif not isinstance(ctx, dict):

return ctx

return render_template(template_name, **ctx)

return decorated_function

return decorator

18.12.4 Endpoint Decorator

When you want to use the werkzeug routing system for more ﬂexibility you need to

map the endpoint as deﬁned in theRule to a view function. This is possible with this

decorator. For example:

from flask import Flask

from werkzeug.routing import Rule

app = Flask(__name__)

app.url_map.add(Rule(/, endpoint=index))

@app.endpoint(index)

def my_index():

return "Hello world"

18.13 Form Validation with WTForms

When you have to work with form data submitted by a browser view code quickly

becomes very hard to read. There are libraries out there designed to make this process

easier to manage. One of them isWTFormswhich we will handle here. If you ﬁnd

yourself in the situation of having many forms, you might want to give it a try.

132

C# Word: How to Extract Text from C# Word in .NET Project

plain text as well as the formatting data to ensure Visual C# sample code for extracting text from powerful & profession imaging controls, PDF document, image

how to extract data from pdf file using java; extract data from pdf c#

VB.NET Word: Extract Text from Microsoft Word Document in VB.NET

locked as static images and the data is inaccessible Guides in VB.NET. Apart from extracting text from powerful & profession imaging controls, PDF document, tiff

extract pdf form data to excel; how to save pdf form data in reader

When you are working with WTForms you have to deﬁne your forms as classes ﬁrst.

Irecommend breaking up the application into multiple modules (Larger Applications)

for that and adding a separate module for the forms.

Getting most of WTForms with an Extension

TheFlask-WTF extension expands onthis pattern and adds a few handful little helpers

that make working with forms and Flask more fun. You can get it fromPyPI.

18.13.1 The Forms

This is an example form for a typical registration page:

from wtforms import t Form, BooleanField, , TextField, PasswordField, validators

class RegistrationForm(Form):

username = TextField(Username, [validators.Length(min=4, max=25)])

email = TextField(Email Address, [validators.Length(min=6, max=35)])

password = PasswordField(New Password, [

validators.Required(),

validators.EqualTo(confirm, message=Passwords must match)

])

confirm = PasswordField(Repeat Password)

accept_tos = BooleanField(I accept the TOS, [validators.Required()])

18.13.2 In the View

In the view function, the usage of this form looks like this:

@app.route(/register, methods=[GET, POST])

def register():

form = RegistrationForm(request.form)

if request.method == POST and form.validate():

user = User(form.username.data, form.email.data,

form.password.data)

db_session.add(user)

flash(Thanks for r registering)

return redirect(url_for(login))

return render_template(register.html, form=form)

Notice that we are implying that the view is using SQLAlchemy here (SQLAlchemy in

Flask) but this is no requirement of course. Adapt the code as necessary.

Things to remember:

1. create the form fromthe request form value if the data is submitted via the HTTP

POST method and args if the data is submitted as GET.

133

VB.NET Image: Demo Code to Read & Capture Code 93 Barcode from

accurate & quick barcode information extracting function, has String In datas Debug.WriteLine(data) Next End & profession imaging controls, PDF document, image

extract data from pdf; extract pdf data to excel

VB.NET TIFF: TIFF Tag Viewer SDK, Read & Edit TIFF Tag Using VB.

page contain the information about data type, count manipulating controls, like TIFF text extracting control to ASP.NET AJAX, Silverlight, Windows Forms as well

exporting pdf form to excel; java read pdf form fields

2. to validate the data, call the validate() method whichwill returnTrue ifthe data

validates, False otherwise.

3. to access individual values from the form, access form.<NAME>.data.

18.13.3 Forms in Templates

Now to the template side. When you pass the form to the templates you can easily

render them there. Look at the following example template to see how easy this is.

WTForms does half the form generation for us already. To make it even nicer, we can

write a macro that renders a ﬁeld with label and a list of errors if there are any.

Here’s an example _formhelpers.html template with such a macro:

{% macro render_field(field) %}

<dt>{{ field.label l }}

<dd>{{ field(**kwargs)|safe }}

{% if field.errors %}

{% for error in field.errors %}

<li>{{ error r }}</li>

{% endfor %}

</ul>

{% endif %}

</dd>

{% endmacro %}

This macro accepts a couple of keyword arguments that are forwarded to WTForm’s

ﬁeld function that renders the ﬁeld for us. The keyword arguments will be in-

serted as HTML attributes. So for example you can call render_field(form.username,

class=’username’) to add a class to the input element. Note that WTForms returns

standard Python unicode strings, so we have to tell Jinja2 that this data is already

HTML escaped with the |safe ﬁlter.

Here the register.html template for the function we used above which takes advantage

of the _formhelpers.html template:

{% from "_formhelpers.html" import render_field %}

<dl>

</dl>

</form>

For more information about WTForms, head over to theWTFormswebsite.

134

18.14 Template Inheritance

The most powerful part of Jinja is template inheritance. Template inheritance allows

you to build a base “skeleton” template that contains all the commonelements of your

site and deﬁnes blocks that child templates can override.

Sounds complicated but is very basic. It’s easiest to understand it by starting with an

example.

18.14.1 Base Template

This template, which we’ll call layout.html, deﬁnes a simple HTML skeleton docu-

ment that you might use for a simple two-column page. It’s the job of “child” tem-

plates to ﬁll the empty blocks with content:

<!doctype html>

<html>

<head>

{% block head %}

<title>{% block title %}{% endblock %} - My Webpage</title>

{% endblock %}

</head>

<body>

<div id="content">{% block content t %}{% endblock %}</div>

{% block footer %}

{% endblock %}

</div>

</body>

</html>

In this example, the {% block %} tags deﬁne four blocks that child templates can ﬁll

in. All the block tag does is tell the template engine that a child template may override

those portions of the template.

18.14.2 Child Template

Achild template might look like this:

{% extends "layout.html" %}

{% block title %}Index{% % endblock %}

{% block head %}

.important { { color: #336699; }

</style>

135

{% endblock %}

{% block content %}

<h1>Index</h1>

Welcome on my awesome homepage.

{% endblock %}

The {% extends %} tag is the key here. It tells the template engine that this template

“extends” another template. When the template system evaluates this template, ﬁrst

it locates the parent. The extends tag must be the ﬁrst tag in the template. To render

the contents of a block deﬁned in the parent template, use {{ super() }}.

18.15 Message Flashing

Good applications and user interfaces are all about feedback. If the user does not get

enough feedback they will probably end up hating the application. Flask provides a

really simple way to give feedback to a user with the ﬂashing system. The ﬂashing

system basically makes it possible to record a message at the end of a request and

access it next request and only next request. This is usually combined with a layout

template that does this.

18.15.1 Simple Flashing

So here is a full example:

from flask import Flask, flash, redirect, , render_template, \

request, url_for

app = Flask(__name__)

app.secret_key = some_secret

@app.route(/)

def index():

return render_template(index.html)

@app.route(/login, methods=[GET, POST])

def login():

error = None

if request.method == POST:

if request.form[username] != admin or \

request.form[password] != secret:

error = Invalid credentials

else:

flash(You were e successfully y logged in)

return redirect(url_for(index))

return render_template(login.html, error=error)

136

if __name__ == "__main__":

app.run()

And here the layout.html template which does the magic:

<!doctype html>

<title>My Application</title>

{% with messages = get_flashed_messages() %}

{% if messages %}

{% for message in messages %}

<li>{{ message }}</li>

{% endfor %}

</ul>

{% endif %}

{% endwith %}

{% block body %}{% % endblock %}

And here the index.html template:

{% extends "layout.html" %}

{% block body %}

<h1>Overview</h1>

{% endblock %}

And of course the login template:

{% extends "layout.html" %}

{% block body %}

<h1>Login</h1>

{% if error %}

<p class=error><strong>Error:</strong> {{ error r }}

{% endif %}

<dl>

<dt>Username:

<dd><input type=text name=username value="{{

request.form.username }}">

<dt>Password:

</dl>

</form>

{% endblock %}

18.15.2 Flashing With Categories

New in version 0.3.

137

It is also possible to provide categories when ﬂashing a message. The default cate-

gory if nothing is provided is ’message’. Alternative categories can be used to give

the user better feedback. For example error messages could be displayed with a red

background.

To ﬂash a message with a different category, just use the second argument to the

flash() function:

flash(uInvalid password d provided, error)

Inside the template you then have to tell the get_flashed_messages() function to also

return the categories. The loop looks slightly different in that situation then:

{% with messages = get_flashed_messages(with_categories=true) %}

{% if messages %}

{% for category, message in messages %}

<li class="{{ category y }}">{{ message }}</li>

{% endfor %}

</ul>

{% endif %}

{% endwith %}

This is just one example of how to render these ﬂashed messages. One might also use

the category to add a preﬁx such as <strong>Error:</strong> to the message.

18.15.3 Filtering Flash Messages

New in version 0.9.

Optionally you can pass a list of categories which ﬁlters the results of

get_flashed_messages(). This is useful if you wish to render each category in a sepa-

rate block.

{% with errors = get_flashed_messages(category_filter=["error"]) %}

{% if errors %}

<ul>

{%- for msg in errors %}

{% endfor -%}

</ul>

</div>

{% endif %}

{% endwith %}

138

18.16 AJAX with jQuery

jQueryisasmallJavaScriptlibrarycommonlyusedtosimplifyworkingwiththeDOM

and JavaScript ingeneral. It is the perfect tool to make web applications more dynamic

by exchanging JSON between server and client.

JSON itself is a very lightweight transport format, very similar to how Python primi-

tives (numbers, strings, dicts and lists) look like which is widely supported and very

easy to parse. It became popular a few years ago and quickly replaced XML as trans-

port format in web applications.

18.16.1 Loading jQuery

In order to use jQuery, you have to download it ﬁrst and place it in the static folder of

your application and then ensure it’s loaded. Ideally you have a layout template that

is used for all pages where you just have to add a script statement to the bottom of

your <body> to load jQuery:

url_for(static, filename=jquery.js) }}"></script>

Another method is using Google’sAJAXLibrariesAPIto load jQuery:

url_for(static, filename=jquery.js) }}">\x3C/script>)</script>

In this case you have to put jQuery into your static folder as a fallback, but it will

ﬁrst try to load it directly from Google. This has the advantage that your website will

probably load faster for users if they went to at least one other website before using

the same jQuery version from Google because it will already be in the browser cache.

18.16.2 Where is My Site?

Do you know where your application is? If you are developing the answer is quite

simple: it’s on localhost port something and directly on the root of that server. But

what if you later decide to move your application to a different location? For example

to http://example.com/myapp? On the server side this never was a problem because

we were using the handy url_for() function that could answer that question for us,

but if we are using jQuery we should not hardcode the path to the application but

make that dynamic, so how can we do that?

Asimple method would be to add a script tag to our page that sets a global variable

to the preﬁx to the root of the application. Something like this:

$SCRIPT_ROOT = {{ request.script_root|tojson|safe }};

</script>

139

The |safe is necessary in Flask before 0.10 so that Jinja does not escape the JSON

encoded string with HTML rules. Usually this would be necessary, but we are inside

ascript block here where different rules apply.

Information for Pros

In HTML the script tag is declared CDATA which means that entities will not be

parsed. Everything until </script> is handled as script. This also means that there

must never be any </ between the script tags. |tojson is kind enough to do the right

thing here and escape slashes for you ({{ "</script>"|tojson|safe }} is rendered as

"<\/script>").

In Flask 0.10 it goes a step further and escapes all HTML tags with unicode escapes.

This makes it possible for Flask to automatically mark the result as HTML safe.

18.16.3 JSON View Functions

Now let’s create a server side function that accepts two URL arguments of numbers

which should be added togetherand thensentback to the application in a JSON object.

This is a really ridiculous example and is something you usually would do on the

client side alone, but a simple example that shows how you would use jQuery and

Flask nonetheless:

from flask import Flask, jsonify, , render_template, , request

app = Flask(__name__)

@app.route(/_add_numbers)

def add_numbers():

a = request.args.get(a, 0, , type=int)

b = request.args.get(b, 0, , type=int)

return jsonify(result=a + b)

@app.route(/)

def index():

return render_template(index.html)

As you can see I also added an index method here that renders a template. This tem-

plate will load jQuery as above and have a little form we can add two numbers and a

link to trigger the function on the server side.

Note that we are using theget() method here which will never fail. If the key is

missing a default value (here 0) is returned. Furthermore it can convert values to a

speciﬁc type (like in our case int). This is especially handy for code thatis triggered by

ascript (APIs, JavaScript etc.) because you don’t need special error reporting in that

case.

140

Documents you may be interested

c# pdf to image : Extracting data from pdf forms to excel control application platform web page azure html web browser Flask14-part345