Hello, I have mild to moderate Java experience, looked at a few Python lessons before, but not unfamiliar with coding or how to pick it up. But, I'm looking for general knowledge about API trading. If there's a good site or tutorial you can link, that'd be great. But as far as basics go: You need an API software, yes? Are there recommendations? These software...run? You hit GO and it executes a loop that you describe, using inputs from your chosen site? Can you control the software once it's running? Do you have to stop it to alter it? Does your computer need to remain on the whole time?
First, the horse: What are you trading? From what platform/DMA? What meets/doesn't meet your needs? Then, the cart: Does it have an API? What languages? etc etc etc.... ooops.
Interesting, so API isn't a generalized format that API softwares can all work with? Does each site/platform have its own languages? I'd be looking at GDAX/Coinbase API. https://docs.pro.coinbase.com/#introduction What needs could not be met? What needs should I consider?
An API is an interface -- that's all. It's like a translator at the U.N. -- there are as many as there are different languages. It allows you to interface with some application you like (and wish to program some bit of, yourself). Whether you wish to duplicate what's already there, or wish to link it some some external object that improves on things, or different data flows, or want to send output somewhere else for special analysis -- that depends on what was built into the API, and what you can then do with those API abilities. So, the Application comes first, then whatever abilities were built into the Interface, THEN what you wish to Program from there.
API's are typically services these days, like webservices (SOAP/xml) or REST-services. But it is also used for internal library-calls, and is just a format for how to communicate. If you're not sure what to use the API for, then you have no need, so better work on your trading plan first. You don't choose API, but broker/exchange, and then often you can reuse libraries or services that already exist, or make your own. Be warned that mechanical trading is not an edge in itself in any way, rather the opposite in fact.
Simply and basically: Online services and desktop applications may offer an API. These API's offer a way for your code to communicate with their services/apps. Your broker may have an API. Using their API, you can request information and issue 'commands.' For example, you could request the last trade price for a ticker symbol. The response to your code may come in the form of text including metadata. You could issue 'commands' as well. Your code could initiate a trade using their API. Here's some documentation explaining the API of a data provider: https://api.tiingo.com/docs/general/overview