How are payment systems written for a website?

Question

Python

It is required to write a payment system for an online store (without intermediaries for each payment method, i.e. without robokassa, interkassa and similar services). Of the payment options, visa, mastercard, yandex.money and webmoney are planned. django is used as a backend (but this is not so important).
I imagine how the payment is arranged.
1. The user selects a payment method, depending on the chosen method, a form is generated with the required fields, into which the data is transferred.
2. Submitting the form and redirecting to the site corresponding to the payment method.
3. Payment, return back to the website of the online store along with payment data, their subsequent processing.
If everything is clear with yandex.money and webmoney, and I quickly found their api and implementation method, then there were difficulties with visa and mastercard (or Sberbank and Alfabank).
How is the payment system written for visa and mastercard or for a specific bank? what is done in this case? (Let's say you need to work with Sberbank and Alfabank).
Thanks in advance for the replies.
UPD: Regarding banks, I realized that you need to look for an acquiring service, but it's still not clear what to do in this case.

Answer 1

How is the payment system written for visa and mastercard or for a particular bank? what is done in this case? (Let's say you need to work with Sberbank and Alfabank).

From personal experience:
a. You come to the office of the bank that has the "Internet acquiring" service, show your legal entity, statutory documents, beneficiaries, turnover from 50 million per month.
* some work with lower speeds, but % will be extremely unprofitable.
** Without a running and working project, going to the bank is pointless.
b. Wait 2-6 weeks until the Bank's Security Service checks everything.
c. Wait 2-4 weeks for the bank to sign the agreement
d. Get details and API documentation of a particular bank.
e. Implement
f. Wait 1-2 weeks until the bank checks that you have everything according to their protocol.
g. Get combat details.
Please note that:
1. If your volumes are less than 50 million+ per month - with a probability of 99% it will be STRONGLY more profitable for you to work through an intermediary. Look at uniteller.ru , payture.com/ru , payler.com - if you are convincing enough in negotiations, it is quite possible to trade them up to 2-2.5% even at low turnovers (1 million-5 million)
2. Direct banking APIs, to put it mildly, are not modern. As a rule, there will be neither a convenient personal account, nor a sane support service - nothing. But there will be checks, paper reporting requirements and other things dear to the heart of the Soviet bureaucrat.
3. Risks when working through an intermediary are in fact minimal. All of the above make payments daily, that is, even if the intermediary closes, you risk the maximum daily turnover.
Taking into account these points, in my opinion, a direct agreement with the bank makes sense if you have such a large turnover - that the difference in tenths of a percent pays for all this hemorrhoids.
In fact, there is a sea of ​​projects with large turnovers (mamba, badoo, etc) who continue to work through the aggregator, minimizing the costs of lawyers, accountants, technical support for the operation of the gateway, etc., etc.

Answer 2

something like this
www.assist.ru/cms/index.htm
in your case, and indeed in any case, you are working with a gate associated with a specific bank
if you are big - then this is the bank gate
if small - then an assist and the like
can be whether to store credit card tokens at home (for rebills and writing off arbitrary amounts) - also depends on a lot of things

Answer 3

https://github.com/thephppleague/omnipay

Answer 4

Difficulties arose with visa and mastercard (or Sberbank and Alfabank)

It just shows that you have a bad idea. You need an acquiring service from a bank and will connect to their gateways, but since you are small, they will either refuse you or they will charge a large commission.

Answer 5

I agree, with a turnover of less than 500K rubles / month, you need to use an aggregator, and working with a bank (rsb.ru low (2.7%) interest was three years ago) costs large amounts. And get ready that payment aggregators and banks do not send all the primary documents. And robokassa / yandex / qiwi / wb even work with physicists.

Answer 6

Emnip, paypal allows you to accept cards. Or allowed