In Flask, what is "request.args" and how is it used?

Question

As a Flask beginner, I can’t understand how request.args is used. I read somewhere that it is used to return values of query string (correct me if I’m wrong) and how many parameters request.args.get() takes.

I know that when I have to store submitted form data, I can use fname = request.form.get("firstname"). Here, only one parameter is passed, whereas the code below takes two parameters.

@app.route("/")
def home():
    cnx = db_connect()
    cur = cnx.cursor()
    output = []

    page = request.args.get('page', 1)

    try:
        page = int(page)
        skip = (page-1)*4
    except:
        abort(404)
   
    stmt_select = "select * from posts limit %s, 4;"
    values=[skip]

    cur.execute(stmt_select,values)
    x=cur.fetchall()

    for row in reversed(x):
        data = {
           "uid":row[0],
           "pid":row[1],
           "subject":row[2],
           "post_content":row[3],
           "date":datetime.fromtimestamp(row[4]),
        }
        output.append(data)
    
    next = page + 1
    previous = page-1
    if previous<1:
    previous=1
    return render_template("home.html", persons=output, next=next, previous=previous)

Please explain why it takes two parameters, and then what its use is.

Asked By: martinho

||

Source

Answer 1

According to the flask.Request.args documents.

flask.Request.args
A MultiDict with the parsed contents of the query string. (The part in the URL after the question mark).

So the args.get() is method get() for MultiDict, whose prototype is as follows:

get(key, default=None, type=None)

In newer version of flask (v1.0.x and v1.1.x), flask.Request.args is an ImmutableMultiDict(an immutable MultiDict), so the prototype and specific method above are still valid.

Answered By: luoluo

Answer 2

request.args is a MultiDict with the parsed contents of the query string.
From the documentation of get method:

get(key, default=None, type=None)

Return the default value if the
requested data doesn’t exist. If type is provided and is a callable it
should convert the value, return it or raise a ValueError if that is
not possible.

Answered By: r-m-n

Answer 3

As a newbie using Flask and Python myself, I think some of the other answers here take for granted that you have a good understanding of the fundamentals. In case you or other readers don’t, I’ll give more context

… request.args returns a "dictionary" object for you. The "dictionary" object is similar to other collection-type of objects in Python, in that it can store many elements in one single object. Therefore the answer to your question

And how many parameters request.args.get() takes.

It will take only one object, a "dictionary" type of object (as stated in the previous answers). This "dictionary" object, however, can have as many elements as needed… (dictionaries have paired elements called Key, Value).

Other collection-type of objects besides "dictionaries", would be "tuple", and "list"… you can run a google search on those and "data structures" in order to learn other Python fundamentals. This answer is based Python; I don’t have an idea if the same applies to other programming languages.

Answered By: alejandro gg

Answer 4

It has some interesting behaviour in some cases that is good to be aware of:

from werkzeug.datastructures import MultiDict

d = MultiDict([("ex1", ""), ("ex2", None)])

d.get("ex1", "alternive")
# returns: ''

d.get("ex2", "alternative")
# returns no visible output of any kind
# It is returning literally None, so if you do:
d.get("ex2", "alternative") is None
# it returns: True

d.get("ex3", "alternative")
# returns: 'alternative'

Answered By: Juha Untinen

In Flask, what is "request.args" and how is it used?

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