How to add path to os.environ["PATH"] for python in Windows 10?

Question

I have a script which has an error because 'neato.exe' can't be found in paths. When I look at os.environ["PATH"], indeed C:\\Program Files (x86)\\Graphviz2.38\\bin, the path to neato.exe, is not there. I can do a hack for the time being by adding this line, but this doesn't seem satisfactory.

if  not 'C:\\Program Files (x86)\\Graphviz2.38\\bin' in os.environ["PATH"]: 
    os.environ["PATH"] += os.pathsep + 'C:\\Program Files (x86)\\Graphviz2.38\\bin' 

Nonetheless, it shows that the error ValueError("Program %s not found in path." neato.exe) is an accurate error. The script works when I add the path to Neato. I added C:\Program Files (x86)\Graphviz2.38\bin to my Environmental Variables in windows, but to no avail. And I also noticed that there are only a few paths in my Path Env. Vars., not the many that python lists. I am using python 3.7 and also running it using the anaconda navigator. I would like to make a more permanent change so I don't have to edit every script that looks for neato.exe with the silly if statement above. Does anyone know how to change what's in os.environ["PATH"] in anaconda?

I am using networkx, networkx.drawing.nx_agraph.to_agraph. The script agraph.py has this function (_which()), which need to make a path match or it will throw an error.

def _which(self, name):
    """Searches for name in exec path and returns full path"""


    import os
    import glob

    paths = os.environ["PATH"]

    if os.name == "nt":
        exe = ".exe"
    else:
        exe = ""
    for path in paths.split(os.pathsep):

        match = glob.glob(os.path.join(path, name + exe))
        if match:
            return match[0]
    raise ValueError("No prog %s in path." % name)

Answer 1

A few things to note about Windows Path:

1. Windows Path is a combination of user defined and system defined - the former is appended to the latter
2. Windows Path has a pretty short length limit

Unfortunately because of the above, you'll probably want to temporarily change the Path for your program to ensure it can find the binary you're looking for.

You could set the PATH environment variable with the Graphviz bin directory at the beginning before executing your script(s).