What is a macro example?

It's when you have an element being displayed in a web browser.

In some cases, we can do this with CSS, but more often than not, we need to manipulate the HTML file. Let's take a simple example of displaying an image, which could be an tag in HTML.

This is simply how you add an image to the body of your HTML code. Your CSS is optional because we will be manipulating this via JavaScript with a class or id attached to the tag. This is just JavaScript (CSS).

. . The src attribute of the tag is important. If we don't add a source to our image, then we'll get an alert saying that a file didn't find. Why is this? You would think that it would find myimage.png in the website root directory, but if we're writing JavaScript or using a front-end framework like Angular or React, they might have additional folders in their root directory, like nodemodules, src, and assets . We need to look at this directory. Here's our folder structure:

So, if we navigate to our image on a different computer or view source, we'll see the folder as we expect; but once we put in myimage.png in the body tag, the alert will tell us that the image doesn't exist.png">
The root source location is going to be whatever the website is on. If we're visiting www.mywebsite.com/index.html, then that's what the source location should be. This may seem like an odd issue because a website does not contain an image. If we are not using a front-end framework or an MVC style PHP web platform, then we want our website to be the only thing containing content for that website. The page of the website, like index.html, will have content inside of it. Our website will not contain the images; instead, we're pulling them in from the website. The root location should be there in the HTML.

Can you do macros in Python?

In the spirit of fun, I ran some macros on a text file.

A few months ago, there was a "What's the macro? Macros" session at PyCon USA that showed some python macros. I decided to have a bit of fun with it and see what I could achieve. Here's the output:

#! system ( "chmod 777 %s" % sys . Argv ) < 2 : print >> sys . Stdout, "Usage: %s " % sys . Readlines ( ) for num in range ( 0, 100 ): with open ( sys . Write ( "%s" % text ) else : t . Format ( str ( num ))) f . Close () t . Close () # end of input - next thing is to count characters. For line in t : line = line . Upper != ch .

What is the difference between a function and a macro in Python?

The answers will vary, but here's mine: a macro is more powerful than a function, and a function can't always do everything you need.

If you want to write macros, use Python 3.7 or newer with PEP238/242 support. And use good judgement (which is a hard concept to describe).

To quote the documentation of the macro package: Macros are a powerful extension mechanism for Python, with which a programmer can produce the implementation of a new language feature directly in Python code. In a way, macro allows Python coders who don't program in another language to produce their own extensions. A function by comparison is strictly meant for writing function bodies. In other words, if you understand how Python operates, you probably don't need a macro unless you're writing your own language, because macros will only allow for more complexity, making it harder to reason about them. The macro package will be of little help to you.

Here's the big problem I'm having while reading and researching articles on macros: we're told macros can: create new language features without creating a programming language. Provide useful language features to Python for free. Generate "better" Python. For example: the def command allows you to define functions that use Python dictionaries as function arguments and return values. But a function, by itself, has no idea how it ought to work internally. While a function may return a value, a real definition of what that value will look like is created through a macro.

With a macro, you can build up the definition as you go.