When should I use "development mode"?

[py_lrnr]

I am new to python and I have come across the following command and its description:

Now to be able to run the project you will need to install it and its >dependencies.

python setup.py develop

I looked up what the 'develop' argument does and found:

Extra commands:
develop install package in 'development mode'

I searched for a description of 'development mode' but could not find a good description.

Can anyone (very briefly) explain to me, in a sentence or two:

what 'development mode' is?
how 'development mode' differs from other 'modes'?
why/when I would use 'development mode'?
what 'development mode' does or does not allow me to do?

Many thanks in advance.

 

[Ian Kelly]

Can anyone (very briefly) explain to me, in a sentence or two:

what 'development mode' is?
how 'development mode' differs from other 'modes'?
why/when I would use 'development mode'?
what 'development mode' does or does not allow me to do?

Instead of installing the package into your site-packages, it installs
a link back to the source folder. This lets you make changes to the
code in the source folder which are immediately visible to Python
without having to install the package again.