just note, The different between the methods are, if the header is not exist

request.headers.get('your-header-name')

will return None or no exception, so you can use it like

if request.headers.get('your-header-name'):
    ....

but the following will throw an error

if request.headers['your-header-name'] # KeyError: 'your-header-name'
    ....

You can handle it by

if 'your-header-name' in request.headers:
   customHeader = request.headers['your-header-name']
   ....

If any one's trying to fetch all headers that were passed then just simply use:

dict(request.headers)

it gives you all the headers in a dict from which you can actually do whatever ops you want to. In my use case I had to forward all headers to another API since the python API was a proxy

Let's see how we get the params, headers and body in Flask. I'm gonna explain with the help of postman.

The params keys and values are reflected in the API endpoint. for example key1 and key2 in the endpoint :

from flask import Flask, request
app = Flask(__name__)

@app.route('/upload')
def upload():

    key_1 = request.args.get('key1')
    key_2 = request.args.get('key2')
    print(key_1)
    #--> value1
    print(key_2)
    #--> value2

After params, let's now see how to get the headers:

header_1 = request.headers.get('header1')
header_2 = request.headers.get('header2')
print(header_1)
#--> header_value1
print(header_2)
#--> header_value2

Now let's see how to get the body

file_name = request.files['file'].filename
ref_id = request.form['referenceId']
print(ref_id)
#--> WWB9838yb3r47484

so we fetch the uploaded files with request.files and text with request.form