Flask: How can I store user's form-input so that it can be retrieved two requests later - forms

Question

I am working on a logistics website using Flask.
On route /step1 the user fills in a form detailing n parcels and their attributes.
The form is submitted and a POST request is sent to /step2 with the following data:
*weight1, length1, width1, height1,
weight2, length2 ...
...
...
*weightn, lengthn, widthn, heightn,
In /step2 the user fills in the sender and recipient addresses.
This form is submitted as a POST request to /process-order
Here's the problem:
How does my process_order view retrieve the data provided in both /step1 and /step2
I can think of three solutions - listed below - but I only know how to go about the first one.
storing the data submitted in step1 form inside hidden inputs and sending this to the form in step2.html and subsequently retrieving this data from the request sent to process_order and storing them as an array.
Caching
flask.g
N.B. This is my very first Flask project and I have zero experience with caching. So please dumb things down for me.
Update
Here's my actual code:
#main.route('/order', methods=['POST'])
def order():
# this function is invoked when user submits a form from the home page
country_from = request.form['country_from']
country_to = request.form['country_to']
data = request.form
parcels = []
for i in range(1, int(data['parcel_count']) + 1):
parcel = Parcel(
weight=data['weight{}'.format(i)],
length=data['length{}'.format(i)],
width=data['width{}'.format(i)],
height=data['height{}'.format(i)],
)
parcels.append(parcel)
weight_units = data['units']
if weight_units == 'kg':
distance_units = 'cm'
else:
distance_units = '"'
return render_template('order.html',
countries = COUNTRIES,
country_from = country_from,
country_to = country_to,
parcels = parcels,
weight_units = weight_units,
distance_units = distance_units,
)
#main.route('/process-order', methods=['POST'])
def process_order():
data = request.form
parcels = []
# pending
# how can I retrieve the parcels array again?
Note that my view functions are being invoked from the action attribute of the forms in my templates (not included here).

Answer 1

Also, you can pass the inputs between steps as parameters as follows
#app.route('/step1', methods=['GET', 'POST'])
def step1():
parcels=[(11,12,13,14),(21,22,23,24),(31,32,33,34)] # contain list of weights, lengths, widths, heights,
weight_units ='kg' # another data to pass
return redirect(url_for('step2',x=parcels,y=weight_units ))
#app.route('/step2/<x>/<y>', methods=['GET', 'POST'])
def step2(x,y):
print(x) # console output
print(y)
return 'ok'
and so on, send all to the next one with more parameters