The following parameters will be used:
- global-env: set it to true to use the global environment
- isolate-env: set it to true to not modify the global environment
Basically, the global environment is the locals() and globals()
shared by all python codes. Unless something like global-env=true is added
to options, a python code do not have access to that environment.
Also, unless something like isolate-env=true is added to options,
the final locals() and globals() of the python code are added to the global env.
First, consider the following code:
```genhtml
message = '<b> This is a message </b>'
```
Unless some magic in footers is invoqued with footer=…, this code will not
print anything, and therefore will be converted to nothing.
However, as explained before, it will change the global environment by adding
a message variable containing a message.
message = '<b> This is a message </b>'
Let's make a new python code that will (1) have access to the global environment and (2) make use of that variable:
```genhtml global-env=true
print(message)
```
Which will be converted as:
print(message)
Now, let's modify the message in an isolated environment:
```genhtml isolated-env=true
message = '<i> This is a message </i>'
print(message)
```
It will yield, as expected:
message = '<i> This is a message </i>'
print(message)
However, if we call again the global-env-enabled code that print the variable message, we get:
print(message)
As if no code modified the message.