A group of entities that can communicate even though they are not directly connected. There has to be at least three entities and there has to be a way that entities that are not directly connected can still communicate.
This Video does a good job of explaining it.
A server is a computer that interacts with a request we make to the computer. For example, whenever we type in "http://www.google.com", we are sending a request to Google's servers to return a website.
Get parameters are included in the URL. Get requests are used for fetching documents. Get parameters have a max URL length. Get parameters are generally ok to cache. Get parameters should not change the server
Post parameters are included in the body. Post parameters are used for updating data or actually making changes. Post parameters have no max length. Post parameters are almost never cached. Post requests are usually destructive in nature.
When you send commands to the server the server will respond with different codes. There are 3 main server response types. 2xx codes indicate Success. 3xx codes indicate a Redirection. or action needs to be taken by the client in order to fulfill the request. 4xx and 5xx codes indicate Error The 4xx codes are intended for cases in which the client seems to have erred, and the 5xx codes for the cases in which the server is aware that the server has erred.
This websiteprovides a great explanation.
Validation is verifying on the server that what we receive is what we expect to receive. If what we receive is different than what we expect we send a message notifying the user.
It is important that we validate the data and send the appropriate response so that the user knows what the problem is and potentially how to fix it going forward. This Video goes into more detail about this topic.
We need to verify what the user enters and confirm if the data is bad. Using something like a drop-down is not enough to ensure that the user is not passing bad data to our form. It is important that we send appropriate responses or messages if the data is bad or incorrect.
This lesson covers this topic in detail.
Templates refer to a library used to build complicated strings (html). Jinja2 is a template library that was used to make this web page. Avoiding repetition is necessary when programming. You want to avoid having to rewrite the same code multiple times.
The syntax for substituting a variable in Jinja is a double curly brace. Substitution is basically just printing the variable. This is a handy way to substitute a string while maintaining cleaner code.
This is a great way to avoid repetition and makes your code more organized and easier to read. This lets you define a base template which you can later plug new HTML into. This is useful when, for example, you want to have a consistent header and footer across your app. Remember better organized code is more readable,easier to fix, easier to share, and harder to break.
This Wikipedia page has a great definition.
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