Environment variables and PATH

See your environment variables

In the macOS Terminal window,

env
env | sort
env | sort | cat -n

In Microsoft Windows,

C:\Users\Myname>set

The Python script

environ.py

Running the script in IDLE on my macOS Catalina 10.15,

USER=mark
DISPLAY=/private/tmp/com.apple.launchd.mKjVnHJWIU/org.macosforge.xquartz:0
LOGNAME=mark
PATH=/usr/bin:/bin:/usr/sbin:/sbin
SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.JcETotCjaJ/Listeners
HOME=/Users/mark
SHELL=/bin/bash
__CF_USER_TEXT_ENCODING=0x1F5:0x0:0x0
TMPDIR=/var/folders/pb/rx_csw656h95vzh_nk8ndt180000gn/T/
XPC_SERVICE_NAME=0
XPC_FLAGS=0x0
LC_CTYPE=UTF-8
PYTHONPATH=/Applications/Python 3.7/IDLE.app/Contents/Resources
DYLD_LIBRARY_PATH=/Applications/Python 3.7/IDLE.app/Contents/Frameworks
DYLD_FRAMEWORK_PATH=/Applications/Python 3.7/IDLE.app/Contents/Frameworks
__PYVENV_LAUNCHER__=/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7

Things to try

Print the environment variables in alphabetical order of the name of each environment variable. In this and the following example, the .keys() is not necessary. But it reminds you that what we’re looping through is the keys of the dictionary.

for key in sorted(os.environ.keys()):
    print(f"{key}={os.environ[key]}")

DISPLAY=/private/tmp/com.apple.launchd.mKjVnHJWIU/org.macosforge.xquartz:0
DYLD_FRAMEWORK_PATH=/Applications/Python 3.7/IDLE.app/Contents/Frameworks
DYLD_LIBRARY_PATH=/Applications/Python 3.7/IDLE.app/Contents/Frameworks
HOME=/Users/mark
LC_CTYPE=UTF-8
LOGNAME=mark
PATH=/usr/bin:/bin:/usr/sbin:/sbin
PYTHONPATH=/Applications/Python 3.7/IDLE.app/Contents/Resources
SHELL=/bin/bash
SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.JcETotCjaJ/Listeners
TMPDIR=/var/folders/pb/rx_csw656h95vzh_nk8ndt180000gn/T/
USER=mark
XPC_FLAGS=0x0
XPC_SERVICE_NAME=0
__CF_USER_TEXT_ENCODING=0x1F5:0x0:0x0
__PYVENV_LAUNCHER__=/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7

Print the environment variables in alphabetical order, numbered starting at 1.

for i, key in enumerate(sorted(os.environ.keys()), start = 1):
    print(f"{i:2} {key}={os.environ[key]}")

 1 DISPLAY=/private/tmp/com.apple.launchd.mKjVnHJWIU/org.macosforge.xquartz:0
 2 DYLD_FRAMEWORK_PATH=/Applications/Python 3.7/IDLE.app/Contents/Frameworks
 3 DYLD_LIBRARY_PATH=/Applications/Python 3.7/IDLE.app/Contents/Frameworks
 4 HOME=/Users/mark
 5 LC_CTYPE=UTF-8
 6 LOGNAME=mark
 7 PATH=/usr/bin:/bin:/usr/sbin:/sbin
 8 PYTHONPATH=/Applications/Python 3.7/IDLE.app/Contents/Resources
 9 SHELL=/bin/bash
10 SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.JcETotCjaJ/Listeners
11 TMPDIR=/var/folders/pb/rx_csw656h95vzh_nk8ndt180000gn/T/
12 USER=mark
13 XPC_FLAGS=0x0
14 XPC_SERVICE_NAME=0
15 __CF_USER_TEXT_ENCODING=0x1F5:0x0:0x0
16 __PYVENV_LAUNCHER__=/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7

Run the script from the macOS Terminal command line.

python3 environ.py
 1 DISPLAY=/private/tmp/com.apple.launchd.mKjVnHJWIU/org.macosforge.xquartz:0
 2 HOME=/Users/mark
 3 LANG=en_US.UTF-8
 4 LOGNAME=mark
 5 OLDPWD=/Users/mark
 6 PATH=/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Apple/usr/bin:/Library/Apple/bin:/opt/X11/bin
 7 PWD=/Users/mark/python
 8 SHELL=/bin/zsh
 9 SHLVL=1
10 SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.JcETotCjaJ/Listeners
11 TERM=xterm-256color
12 TERM_PROGRAM=Apple_Terminal
13 TERM_PROGRAM_VERSION=433
14 TERM_SESSION_ID=7EDE954C-CDD0-4EDC-B406-C60426B468B5
15 TMPDIR=/var/folders/pb/rx_csw656h95vzh_nk8ndt180000gn/T/
16 USER=mark
17 XPC_FLAGS=0x0
18 XPC_SERVICE_NAME=0
19 _=/usr/local/bin/python3
20 __CF_USER_TEXT_ENCODING=0x1F5:0x0:0x0
21 __PYVENV_LAUNCHER__=/usr/local/bin/python3

Run the script on the Fedora Linux box oit2.scps.nyu.edu.

python3 environ.py
 1 HISTCONTROL=ignoredups
 2 HISTSIZE=1000
 3 HOME=/home/m/meretzkm
 4 HOSTNAME=oit2.scps.nyu.edu
 5 LANG=en_US.UTF-8
 6 LD_LIBRARY_PATH=/home/m/meretzkm/web/glut-3.7/lib/glut
 7 LESSOPEN=||/usr/bin/lesspipe.sh %s
 8 LIBGL_ALWAYS_INDIRECT=1
 9 LOGNAME=meretzkm
10 LS_COLORS=rs=0:di=38;5;33:ln=38;5;51:mh=00:pi=40;38;5;11:so=38;5;13:do=38;5;5:bd=48;5;232;38;5;11:cd=48;5;232;38;5;3:or=48;5;232;38;5;9:mi=01;05;37;41:su=48;5;196;38;5;15:sg=48;5;11;38;5;16:ca=48;5;196;38;5;226:tw=48;5;10;38;5;16:ow=48;5;10;38;5;21:st=48;5;21;38;5;15:ex=38;5;40:*.tar=38;5;9:*.tgz=38;5;9:*.arc=38;5;9:*.arj=38;5;9:*.taz=38;5;9:*.lha=38;5;9:*.lzh=38;5;9:*.lzma=38;5;9:*.tlz=38;5;9:*.txz=38;5;9:*.tzo=38;5;9:*.t7z=38;5;9:*.zip=38;5;9:*.z=38;5;9:*.Z=38;5;9:*.dz=38;5;9:*.gz=38;5;9:*.lrz=38;5;9:*.lz=38;5;9:*.lzo=38;5;9:*.xz=38;5;9:*.bz2=38;5;9:*.bz=38;5;9:*.tbz=38;5;9:*.tbz2=38;5;9:*.tz=38;5;9:*.deb=38;5;9:*.rpm=38;5;9:*.jar=38;5;9:*.war=38;5;9:*.ear=38;5;9:*.sar=38;5;9:*.rar=38;5;9:*.alz=38;5;9:*.ace=38;5;9:*.zoo=38;5;9:*.cpio=38;5;9:*.7z=38;5;9:*.rz=38;5;9:*.cab=38;5;9:*.jpg=38;5;13:*.jpeg=38;5;13:*.gif=38;5;13:*.bmp=38;5;13:*.pbm=38;5;13:*.pgm=38;5;13:*.ppm=38;5;13:*.tga=38;5;13:*.xbm=38;5;13:*.xpm=38;5;13:*.tif=38;5;13:*.tiff=38;5;13:*.png=38;5;13:*.svg=38;5;13:*.svgz=38;5;13:*.mng=38;5;13:*.pcx=38;5;13:*.mov=38;5;13:*.mpg=38;5;13:*.mpeg=38;5;13:*.m2v=38;5;13:*.mkv=38;5;13:*.ogm=38;5;13:*.mp4=38;5;13:*.m4v=38;5;13:*.mp4v=38;5;13:*.vob=38;5;13:*.qt=38;5;13:*.nuv=38;5;13:*.wmv=38;5;13:*.asf=38;5;13:*.rm=38;5;13:*.rmvb=38;5;13:*.flc=38;5;13:*.avi=38;5;13:*.fli=38;5;13:*.flv=38;5;13:*.gl=38;5;13:*.dl=38;5;13:*.xcf=38;5;13:*.xwd=38;5;13:*.yuv=38;5;13:*.cgm=38;5;13:*.emf=38;5;13:*.ogv=38;5;13:*.ogx=38;5;13:*.aac=38;5;45:*.au=38;5;45:*.flac=38;5;45:*.m4a=38;5;45:*.mid=38;5;45:*.midi=38;5;45:*.mka=38;5;45:*.mp3=38;5;45:*.mpc=38;5;45:*.ogg=38;5;45:*.ra=38;5;45:*.wav=38;5;45:*.oga=38;5;45:*.opus=38;5;45:*.spx=38;5;45:*.xspf=38;5;45:
11 MAIL=/var/spool/mail/meretzkm
12 OLDPWD=/home/m/meretzkm
13 PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/m/meretzkm/.local/bin:/home/m/meretzkm/bin:/home/m/meretzkm/.local/glut/bin:/home/m/meretzkm/.local/gnome/bin:/home/m/meretzkm/.local/gtk/bin:/home/m/meretzkm/.local/kde/bin
14 PWD=/home/m/meretzkm/public_html/python/dict
15 QT_GRAPHICSSYSTEM_CHECKED=1
16 SHELL=/bin/bash
17 SHLVL=1
18 SSH_ASKPASS=/usr/libexec/openssh/gnome-ssh-askpass
19 SSH_CLIENT=66.108.88.87 64513 22
20 SSH_CONNECTION=66.108.88.87 64513 128.122.238.18 22
21 SSH_TTY=/dev/pts/0
22 TERM=xterm-256color
23 TMP=/tmp
24 USER=meretzkm
25 XDG_RUNTIME_DIR=/run/user/1153
26 XDG_SESSION_ID=243392
27 _=/usr/local/bin/python3

On Microsoft Windows 10:

 1 ALLUSERSPROFILE=C:\ProgramData
 2 APPDATA=C:\Users\madan\AppData\Roaming
 3 COMMONPROGRAMFILES=C:\Program Files (x86)\Common Files
 4 COMMONPROGRAMFILES(X86)=C:\Program Files (x86)\Common Files
 5 COMMONPROGRAMW6432=C:\Program Files\Common Files
 7 COMPUTERNAME=DESKTOP-P9PKRMD
 8 COMSPEC=C:\WINDOWS\system32\cmd.exe
 9 HOME=C:\Users\madan
10 HOMEDRIVE=C:
11 HOMEPATH=\Users\madan
12 LOCALAPPDATA=C:\Users\madan\AppData\Local
13 LOGONSERVER=\\DESKTOP-P9PKRMD
14 NUMBER_OF_PROCESSORS=4
15 ONEDRIVE=C:\Users\madan\OneDrive
16 OS=Windows_NT
17 PATH=C:\Program Files (x86)\Intel\iCLS Client\;C:\Program Files\Intel\iCLS Client\;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files\Intel\WiFi\bin\;C:\Program Files\Common Files\Intel\WirelessCommon\;C:\Users\madan\AppData\Local\Microsoft\WindowsApps;
18 PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
19 PROCESSOR_ARCHITECTURE=x86
20 PROCESSOR_ARCHITEW6432=AMD64
21 PROCESSOR_IDENTIFIER=Intel64 Family 6 Model 78 Stepping 3, GenuineIntel
22 PROCESSOR_LEVEL=6
23 PROCESSOR_REVISION=4e03
24 PROGRAMDATA=C:\ProgramData
25 PROGRAMFILES=C:\Program Files (x86)
26 PROGRAMFILES(X86)=C:\Program Files (x86)
27 PROGRAMW6432=C:\Program Files
28 PSMODULEPATH=C:\Program Files\WindowsPowerShell\Modules;C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules
29 PUBLIC=C:\Users\Public
30 SESSIONNAME=Console
31 SYSTEMDRIVE=C:
32 SYSTEMROOT=C:\WINDOWS
33 TEMP=C:\Users\madan\AppData\Local\Temp
34 TMP=C:\Users\madan\AppData\Local\Temp
35 USERDOMAIN=DESKTOP-P9PKRMD
36 USERDOMAIN_ROAMINGPROFILE=DESKTOP-P9PKRMD
37 USERNAME=madan
38 USERPROFILE=C:\Users\madan
39 WINDIR=C:\WINDOWS

List the directories in the PATH environment variable, one per line. Do not sort them.

import sys
import os

try:
    path = os.environ["PATH"]          #path is a string.
except KeyError:
    print("Couldn't find the PATH environment variable.", file = sys.stderr)
    sys.exit(1)

print(f'PATH = "{path}"')
print(f'os.pathsep = "{os.pathsep}"')  #pathsep is a one-character string.
print()

directories = path.split(os.pathsep)   #directories is a list of strings.

for i, directory in enumerate(directories, start = 1):
    print(f"{i:2} {directory}")

In IDLE on macOS Catalina 10.15,

PATH = "/usr/bin:/bin:/usr/sbin:/sbin"
os.pathsep = ":"

 1 /usr/bin
 2 /bin
 3 /usr/sbin
 4 /sbin

From the Terminal on macOS Catalina 10.15:

PATH = "/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Apple/usr/bin:/Library/Apple/bin:/opt/X11/bin"
os.pathsep = ":"

 1 /usr/local/bin
 2 /usr/bin
 3 /bin
 4 /usr/sbin
 5 /sbin
 6 /Library/Apple/usr/bin
 7 /Library/Apple/bin
 8 /opt/X11/bin

From the shell window on the Fedora Linux machine oit2.spcs.nyu.edu:

PATH = "/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/m/meretzkm/.local/bin:/home/m/meretzkm/bin:/home/m/meretzkm/.local/glut/bin:/home/m/meretzkm/.local/gnome/bin:/home/m/meretzkm/.local/gtk/bin:/home/m/meretzkm/.local/kde/bin"
os.pathsep = ":"

 1 /usr/local/bin
 2 /usr/bin
 3 /usr/local/sbin
 4 /usr/sbin
 5 /home/m/meretzkm/.local/bin
 6 /home/m/meretzkm/bin
 7 /home/m/meretzkm/.local/glut/bin
 8 /home/m/meretzkm/.local/gnome/bin
 9 /home/m/meretzkm/.local/gtk/bin
10 /home/m/meretzkm/.local/kde/bin

On my Microsoft Windows 7 Home Premium (missing the first lines of output, sorry):

 1 C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common
 2 C:\Program Files\Common Files\Microsoft Shared\Windows Live
 3 C:\Program Files (x86)\Common Files\Microsoft Shared\Windows Live
 4 C:\windows\system32
 5 C:\windows
 6 C:\windows\System32\Wbem
 7 C:\windows\System32\WindowsPowerShell\v1.0\
 8 C:\Program Files (x86)\Windows Live\Shared
 9 C:\Program Files (x86)\Toshiba\Bluetooth Toshiba Stack\sys\
10 C:\Program Files (x86)\Toshiba\Bluetooth Toshiba Stack\sys\x64\
11 C:\Users\Mark\Development\adt-bundle-windows-x86_64-20140702\sdk\tools
12 C:\Users\Mark\Development\adt-bundle-windows-x86_64-20140702\sdk\platform-tools
13 C:\Program Files (x86)\QuickTime\QTSystem\
14 C:\Users\Mark\AppData\Local\Programs\Python\Python36-32
15 C:\Users\Mark\python