Get the value of a checkbox in Flask

Question

I want to get the value of a checkbox in Flask. I’ve read a similar post and tried to use the output of request.form.getlist('match') and since it’s a list I use [0], but it seems I’m doing something wrong. Is this the correct way to get the output or is there a better way?

<input type="checkbox" name="match" value="matchwithpairs" checked> Auto Match

if request.form.getlist('match')[0] == 'matchwithpairs':
    # do something

Asked By: Jaquacky

||

Source

Answer 1

You don’t need to use getlist, just get if there’s only one input with the given name, although it shouldn’t matter. What you’ve shown does work. Here’s a simple runnable example:

from flask import Flask, request

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
    if request.method == 'POST':
        print(request.form.getlist('hello'))

    return '''<form method="post">
<input type="checkbox" name="hello" value="world" checked>
<input type="checkbox" name="hello" value="davidism" checked>
<input type="submit">
</form>'''

app.run()

Submitting the form with both boxes checked prints ['world', 'davidism'] in the terminal. Note that the html form’s method is post so that the data will be in request.form.

While there are some cases where knowing the actual value or list of values of an field is useful, it looks like all you care about is whether the box was checked. In this case, it’s more common to give the checkbox a unique name and just check if it has any value at all.

<input type="checkbox" name="match-with-pairs"/>
<input type="checkbox" name="match-with-bears"/>

if request.form.get('match-with-pairs'):
    # match with pairs

if request.form.get('match-with-bears'):
    # match with bears (terrifying)

Answered By: davidism

Answer 2

I found 4 ways to do that: Just to summarize:

# first way
op1 = request.form.getlist('opcao1') # [u'Item 1'] []
op2 = request.form.getlist('opcao2') # [u'Item 2'] []
op3 = request.form.getlist('opcao3') # [u'Item 3'] []

# second
op1_checked = request.form.get("opcao1") != None
op2_checked = request.form.get("opcao2") != None
op3_checked = request.form.get("opcao3") != None

# third
if request.form.get("opcao3"):
    op1_checked = True

# fourth
op1_checked, op1_checked, op1_checked = False, False, False
if request.form.get("opcao1"):
    op1_checked = True
if request.form.get("opcao2"):
    op2_checked = True
if request.form.get("opcao3"):
    op3_checked = True

# last way that I found ..
op1_checked = "opcao1" in request.form
op2_checked = "opcao2" in request.form
op3_checked = "opcao3" in request.form

Answered By: Silas Santiago

Answer 3

When working with checkboxes in Flask, I opt to use the .get() method. This is because in my case (as is the case with checkboxes), the value of the checkbox returned is either ‘on’ or ‘None’ Consider the cases below:

A common way of getting form data on POST request. When working with checkboxes, the solution below fails:
```
username = request.form["uname"]
```
Using the get method. This one works since the results from the form are in the form of a dictionary. The get method doesn’t break when that value is None (as is the case with an unchecked checkbox):
```
username = request.form.get("uname")
```

Answered By: Engineer Lenny

Get the value of a checkbox in Flask

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