Question

[Solved] In Flask, What is request.args and how is it used?

I’m new in Flask. 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.

Consider this code. Pagination has also been done in this code.

@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)

Here, request.args.get() takes two parameters. Please explain why it takes two parameters and what is the use of it.

Enquirer: martinho

||

Solution #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)

Update:
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 is still valid.

Respondent: luoluo

Solution #2:

@martinho as a newbie using Flask and Python myself, I think the previous answers here took for granted that you had a good understanding of the fundamentals. In case you or other viewers don’t know the fundamentals, I’ll give more context to understand the answer…

… the request.args is bringing 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.

Respondent: alejandro gg

Solution #3:

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.

Respondent: r-m-n

Solution #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'
Respondent: Juha Untinen

The answers/resolutions are collected from stackoverflow, are licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 .

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