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How do you access query parameters or the query string in Flask routes? It's not obvious from the Flask documentation.
The example route /data below illustrates the context that I would like to access that data. If someone requests something like example.com/data?abc=123, I would like access to the string ?abc=123 or to be able to retrieve the value of parameters like abc.
#app.route("/data")
def data():
# query_string = ???
return render_template("data.html")
from flask import request
#app.route('/data')
def data():
# here we want to get the value of user (i.e. ?user=some-value)
user = request.args.get('user')
The full URL is available as request.url, and the query string is available as request.query_string.decode().
Here's an example:
from flask import request
#app.route('/adhoc_test/')
def adhoc_test():
return request.query_string
To access an individual known param passed in the query string, you can use request.args.get('param'). This is the "right" way to do it, as far as I know.
ETA: Before you go further, you should ask yourself why you want the query string. I've never had to pull in the raw string - Flask has mechanisms for accessing it in an abstracted way. You should use those unless you have a compelling reason not to.
I came here looking for the query string, not how to get values from the query string.
request.query_string returns the URL parameters as raw byte string (Ref 1).
Example of using request.query_string:
from flask import Flask, request
app = Flask(__name__)
#app.route('/data', methods=['GET'])
def get_query_string():
return request.query_string
if __name__ == '__main__':
app.run(debug=True)
Output:
References:
Official API documentation on query_string
We can do this by using request.query_string.
Example:
Lets consider view.py
from my_script import get_url_params
#app.route('/web_url/', methods=('get', 'post'))
def get_url_params_index():
return Response(get_url_params())
You also make it more modular by using Flask Blueprints - https://flask.palletsprojects.com/en/1.1.x/blueprints/
Lets consider first name is being passed as a part of query string
/web_url/?first_name=john
## here is my_script.py
## import required flask packages
from flask import request
def get_url_params():
## you might further need to format the URL params through escape.
firstName = request.args.get('first_name')
return firstName
As you see this is just a small example - you can fetch multiple values + formate those and use it or pass it onto the template file.
Werkzeug/Flask as already parsed everything for you. No need to do the same work again with urlparse:
from flask import request
#app.route('/')
#app.route('/data')
def data():
query_string = request.query_string ## There is it
return render_template("data.html")
The full documentation for the request and response objects is in Werkzeug: http://werkzeug.pocoo.org/docs/wrappers/
Try like this for query string:
from flask import Flask, request
app = Flask(__name__)
#app.route('/parameters', methods=['GET'])
def query_strings():
args1 = request.args['args1']
args2 = request.args['args2']
args3 = request.args['args3']
return '''<h1>The Query String are...{}:{}:{}</h1>''' .format(args1,args2,args3)
if __name__ == '__main__':
app.run(debug=True)
Output:
Every form of the query string retrievable from flask request object as described in O'Reilly Flask Web Devleopment:
From O'Reilly Flask Web Development, and as stated by Manan Gouhari earlier, first you need to import request:
from flask import request
request is an object exposed by Flask as a context variable named (you guessed it) request. As its name suggests, it contains all the information that the client included in the HTTP request. This object has many attributes and methods that you can retrieve and call, respectively.
You have quite a few request attributes which contain the query string from which to choose. Here I will list every attribute that contains in any way the query string, as well as a description from the O'Reilly book of that attribute.
First there is args which is "a dictionary with all the arguments passed in the query string of the URL." So if you want the query string parsed into a dictionary, you'd do something like this:
from flask import request
#app.route('/'):
queryStringDict = request.args
(As others have pointed out, you can also use .get('<arg_name>') to get a specific value from the dictionary)
Then, there is the form attribute, which does not contain the query string, but which is included in part of another attribute that does include the query string which I will list momentarily. First, though, form is "A dictionary with all the form fields submitted with the request." I say that to say this: there is another dictionary attribute available in the flask request object called values. values is "A dictionary that combines the values in form and args." Retrieving that would look something like this:
from flask import request
#app.route('/'):
formFieldsAndQueryStringDict = request.values
(Again, use .get('<arg_name>') to get a specific item out of the dictionary)
Another option is query_string which is "The query string portion of the URL, as a raw binary value." Example of that:
from flask import request
#app.route('/'):
queryStringRaw = request.query_string
Then as an added bonus there is full_path which is "The path and query string portions of the URL." Por ejemplo:
from flask import request
#app.route('/'):
pathWithQueryString = request.full_path
And finally, url, "The complete URL requested by the client" (which includes the query string):
from flask import request
#app.route('/'):
pathWithQueryString = request.url
Happy hacking :)
I prefer
user = request.args['user'] if 'user' in request.args else 'guest'
over
user = request.args.get('user')
this way, you can check the url actually contains the query string first
The implementation below worked for me.
from flask import request
def getVerificationStatus():
try:
requestId=int(request.args.get('requestId'))
print(requestId)
status= verificationStepRepository.getVerificationStatus(requestId)
return tb.responsify(200, "success", status)
except Exception as e:
return errorHandler.dispatchInternalServerError(str(e))
Often we just want to map the whole query string into an appropriate python data structure and take it from there. The appropriate structure is a multi-dictionary because keywords can repeat, for example we need to handle A=123&A=456&B=789. A multi-dictionary is a list of 2-tuples where each 2-tuple contains the key as its first item and the list of values as its second, so the above goes to [('A',['123','456']),('B',['789'])]. All of this is achieved by
qstr = request.args.lists() # A generator for the multi-dict
qstr = list(qstr) # To get the actual multi-dict
If all you want is a dictionary where the first occurrence of a duplicate keyword is used you can just go
qstr = request.args.to_dict()
This can be done using request.args.get().
For example if your query string has a field date, it can be accessed using
date = request.args.get('date')
Don't forget to add "request" to list of imports from flask,
i.e.
from flask import request
If the request if GET and we passed some query parameters then,
fro`enter code here`m flask import request
#app.route('/')
#app.route('/data')
def data():
if request.method == 'GET':
# Get the parameters by key
arg1 = request.args.get('arg1')
arg2 = request.args.get('arg2')
# Generate the query string
query_string="?arg1={0}&arg2={1}".format(arg1, arg2)
return render_template("data.html", query_string=query_string)
This Code worked for me:
from flask import Flask, request
app = Flask(__name__)
#app.route('/')
def search():
query = request.args
for key,value in query.items():
print(key,value)
return "Hello World"
if __name__ == '__main__':
app.run(debug=True)
the api should include one function called "write text to file" and inputs a string parameter
as for the function to write to the disk I have no problem and I implemented the code my problem is how to set the rest API using python.
EDIT:
this is my code:
from flask import (
Flask,
render_template
)
import SocketServer
import SimpleHTTPServer
import re
app = Flask(__name__, template_folder="templates")
#app.route('/index', methods=['GET'])
def index():
return 'Welcome'
#app.route('/write_text_to_file', methods=['POST'])
def write_text_to_file():
f = open("str.txt", "w+")
f.write("hello world")
f.close()
if __name__ == '__main__':
app.run(debug=True)
anyhow when I try to test my rest api:
http://127.0.0.1:5000/write_text_to_file
I am getting the following error:
Now I'm trying to test my rest-api , however how can I make my code to start the server and to the test the post request api, this is my test_class:
import requests
import unittest
API_ENDPOINT="http://127.0.0.1:5000/write_text_to_file"
class test_my_rest_api(unittest.TestCase):
def test_post_request(self):
"""start the server"""
r = requests.post(API_ENDPOINT)
res = r.text
print(res)
also when runnning my request using postman I am getting internal_server_error:
You're doing a GET request for this url, but you've specified that this endpoint can only accept POST:
#app.route('/write_text_to_file', methods=['POST'])
Also, the SocketServer and SimpleHTTPServer imports are not needed with Flask.
The method is not allowed because Chrome (or any browser) makes GET requests.
Whereas, you defined it as POST
#app.route('/write_text_to_file', methods=['POST'])
Either change it to a GET method, or use a tool such as POSTMan to perform other HTTP call types
How do you access query parameters or the query string in Flask routes? It's not obvious from the Flask documentation.
The example route /data below illustrates the context that I would like to access that data. If someone requests something like example.com/data?abc=123, I would like access to the string ?abc=123 or to be able to retrieve the value of parameters like abc.
#app.route("/data")
def data():
# query_string = ???
return render_template("data.html")
from flask import request
#app.route('/data')
def data():
# here we want to get the value of user (i.e. ?user=some-value)
user = request.args.get('user')
The full URL is available as request.url, and the query string is available as request.query_string.decode().
Here's an example:
from flask import request
#app.route('/adhoc_test/')
def adhoc_test():
return request.query_string
To access an individual known param passed in the query string, you can use request.args.get('param'). This is the "right" way to do it, as far as I know.
ETA: Before you go further, you should ask yourself why you want the query string. I've never had to pull in the raw string - Flask has mechanisms for accessing it in an abstracted way. You should use those unless you have a compelling reason not to.
I came here looking for the query string, not how to get values from the query string.
request.query_string returns the URL parameters as raw byte string (Ref 1).
Example of using request.query_string:
from flask import Flask, request
app = Flask(__name__)
#app.route('/data', methods=['GET'])
def get_query_string():
return request.query_string
if __name__ == '__main__':
app.run(debug=True)
Output:
References:
Official API documentation on query_string
We can do this by using request.query_string.
Example:
Lets consider view.py
from my_script import get_url_params
#app.route('/web_url/', methods=('get', 'post'))
def get_url_params_index():
return Response(get_url_params())
You also make it more modular by using Flask Blueprints - https://flask.palletsprojects.com/en/1.1.x/blueprints/
Lets consider first name is being passed as a part of query string
/web_url/?first_name=john
## here is my_script.py
## import required flask packages
from flask import request
def get_url_params():
## you might further need to format the URL params through escape.
firstName = request.args.get('first_name')
return firstName
As you see this is just a small example - you can fetch multiple values + formate those and use it or pass it onto the template file.
Werkzeug/Flask as already parsed everything for you. No need to do the same work again with urlparse:
from flask import request
#app.route('/')
#app.route('/data')
def data():
query_string = request.query_string ## There is it
return render_template("data.html")
The full documentation for the request and response objects is in Werkzeug: http://werkzeug.pocoo.org/docs/wrappers/
Try like this for query string:
from flask import Flask, request
app = Flask(__name__)
#app.route('/parameters', methods=['GET'])
def query_strings():
args1 = request.args['args1']
args2 = request.args['args2']
args3 = request.args['args3']
return '''<h1>The Query String are...{}:{}:{}</h1>''' .format(args1,args2,args3)
if __name__ == '__main__':
app.run(debug=True)
Output:
Every form of the query string retrievable from flask request object as described in O'Reilly Flask Web Devleopment:
From O'Reilly Flask Web Development, and as stated by Manan Gouhari earlier, first you need to import request:
from flask import request
request is an object exposed by Flask as a context variable named (you guessed it) request. As its name suggests, it contains all the information that the client included in the HTTP request. This object has many attributes and methods that you can retrieve and call, respectively.
You have quite a few request attributes which contain the query string from which to choose. Here I will list every attribute that contains in any way the query string, as well as a description from the O'Reilly book of that attribute.
First there is args which is "a dictionary with all the arguments passed in the query string of the URL." So if you want the query string parsed into a dictionary, you'd do something like this:
from flask import request
#app.route('/'):
queryStringDict = request.args
(As others have pointed out, you can also use .get('<arg_name>') to get a specific value from the dictionary)
Then, there is the form attribute, which does not contain the query string, but which is included in part of another attribute that does include the query string which I will list momentarily. First, though, form is "A dictionary with all the form fields submitted with the request." I say that to say this: there is another dictionary attribute available in the flask request object called values. values is "A dictionary that combines the values in form and args." Retrieving that would look something like this:
from flask import request
#app.route('/'):
formFieldsAndQueryStringDict = request.values
(Again, use .get('<arg_name>') to get a specific item out of the dictionary)
Another option is query_string which is "The query string portion of the URL, as a raw binary value." Example of that:
from flask import request
#app.route('/'):
queryStringRaw = request.query_string
Then as an added bonus there is full_path which is "The path and query string portions of the URL." Por ejemplo:
from flask import request
#app.route('/'):
pathWithQueryString = request.full_path
And finally, url, "The complete URL requested by the client" (which includes the query string):
from flask import request
#app.route('/'):
pathWithQueryString = request.url
Happy hacking :)
I prefer
user = request.args['user'] if 'user' in request.args else 'guest'
over
user = request.args.get('user')
this way, you can check the url actually contains the query string first
The implementation below worked for me.
from flask import request
def getVerificationStatus():
try:
requestId=int(request.args.get('requestId'))
print(requestId)
status= verificationStepRepository.getVerificationStatus(requestId)
return tb.responsify(200, "success", status)
except Exception as e:
return errorHandler.dispatchInternalServerError(str(e))
Often we just want to map the whole query string into an appropriate python data structure and take it from there. The appropriate structure is a multi-dictionary because keywords can repeat, for example we need to handle A=123&A=456&B=789. A multi-dictionary is a list of 2-tuples where each 2-tuple contains the key as its first item and the list of values as its second, so the above goes to [('A',['123','456']),('B',['789'])]. All of this is achieved by
qstr = request.args.lists() # A generator for the multi-dict
qstr = list(qstr) # To get the actual multi-dict
If all you want is a dictionary where the first occurrence of a duplicate keyword is used you can just go
qstr = request.args.to_dict()
This can be done using request.args.get().
For example if your query string has a field date, it can be accessed using
date = request.args.get('date')
Don't forget to add "request" to list of imports from flask,
i.e.
from flask import request
If the request if GET and we passed some query parameters then,
fro`enter code here`m flask import request
#app.route('/')
#app.route('/data')
def data():
if request.method == 'GET':
# Get the parameters by key
arg1 = request.args.get('arg1')
arg2 = request.args.get('arg2')
# Generate the query string
query_string="?arg1={0}&arg2={1}".format(arg1, arg2)
return render_template("data.html", query_string=query_string)
This Code worked for me:
from flask import Flask, request
app = Flask(__name__)
#app.route('/')
def search():
query = request.args
for key,value in query.items():
print(key,value)
return "Hello World"
if __name__ == '__main__':
app.run(debug=True)
I have created an application that uses commandline and call the program.
from flask import Flask, jsonify, make_response, request
import os
import subprocess
import json
app = Flask(__name__)
#app.route('/api/v1.0/qanda/', methods=['GET'])
def people_api():
text = request.args.get('text')
Answer = subprocess.Popen(['programcall', repr(text)],stdout=subprocess.PIPE,stderr=subprocess.PIPE).communicate()[0]
if text is None:
make_response(jsonify({'error': 'Missing text parameter'}), 400)
return jsonify(Answer)
app.run('0.0.0.0')
What I am trying to get is the PRETTY JSON OUTPUT on the application when I hit the browser URL. I tried to display the output but it was not pretty Json and most of the time jsonify was giving error: JSON is not serialized.
Kindly show me the way through which I can display the proper result using my application
One error which I can across is this:
Answer = Answer + subprocess.Popen(['programcall', repr(text)],stdout=subprocess.PIPE,stderr=subprocess.PIPE).communicate()[0]
TypeError: can only concatenate list (not "bytes") to list
You need to wait for your subprocess to finish before you can read the output. That is why sometimes you get the error and sometimes not because sometimes the process finishes and you have the output.
I have a decently intermediate understanding of APIs, and am not trying to host information I've got from APIs onto the web.
This incredibly simple code:
from flask import Flask, request, render_template
import requests
app = Flask(__name__)
#app.route('/temperature', methods=['POST'])
def temperature():
zipcode = request.form['zip']
r = requests.get('http://api.openweathermap.org/data/2.5/weather?zip=' +zipcode+',us&appid=9b56b06ab4c7f06821ccf55e3e10fce5')
json_obj = r.text
return json_obj
#app.route('/')
def index():
return 'hi'
if __name__ == '__main__':
app.run(debug=True)
Is not giving me anything (except the 405 error).
Can someone please explain why my POST method is not working?
While I'm not entirely sure what you have done, here's what I think you did:
You accessed the /temperature page in your browser which is by default a GET-Request.
You then get returned a 405 Method Not Allowed Error, because your route explicitly requires that the page will be accessed via the HTTP-POST Method.
Modify #app.route('/temperature', methods=['POST']) to #app.route('/temperature', methods=['POST', 'GET']) and you should be fine.
I'll post my answer from /r/ flask here, just for posterity.
the line in your code: zipcode = request.form['zip'] implies that you are submitting data from an HTML form to the view via a POST.
If there is no form, then request.form['zip'] does nothing, and is most likely raising the error. Considering that I see no route in your logic there that points to any HTML, I'm guessing that's the issue.
If you have not built a form for the user to submit the zip code, then you could build it into the route logic. For example, you could do:
#app.route('/temperature/<zipcode>')
def temperature(zipcode):
# add some kind of validation here to make sure it's a valid zipcode
r = requests.get('http://api.openweathermap.org/data/2.5/weather?zip=' +zipcode+',us&appid=DONT_SHARE_YOUR_API_KEY')
json_obj = r.text
return json_obj
You could then use http://127.0.0.1:5000/temperature/20003 to see the data for that zip code.
(as a side note, it's often unwise to publicly share your API keys. you may want to generate a new key.)