Python: Environment variables
Python Basic: Exercise-53 with Solution
Write a python program to access environment variables.
Sample Solution-1:
Python Code:
import os
# Access all environment variables
print('*----------------------------------*')
print(os.environ)
print('*----------------------------------*')
# Access a particular environment variable
print(os.environ['HOME'])
print('*----------------------------------*')
print(os.environ['PATH'])
print('*----------------------------------*')
Sample Output:
*----------------------------------*
environ({'LESSOPEN': '| /usr/bin/lesspipe %s', '_': '/usr/bin/timeout', 'LIBVIRT_DEFAULT_URI': 'qemu:///system
', 'HOME': '/home/students', 'TERM': 'xterm-256color', 'SHELL': '/bin/bash', 'SHLVL': '2', 'USER': 'students',
'MAIL': '/var/mail/students', 'COMP_WORDBREAKS': ' \t\n"\'><;|&(:', 'PATH': '/usr/local/bin:/usr/bin:/bin:/us
r/local/games:/usr/games', 'LANG': 'en_US.UTF-8', 'LOGNAME': 'students', 'LS_COLORS': 'rs=0:di=01;34:ln=01;36:
mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=00:su=37;41:sg=30;43:ca=30;41:tw=30;42
:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;3
1:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.d
z=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;
31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:
*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.
bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.p
ng=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.m
kv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wm
v=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01
;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36
:*.flac=00;36:*.m4a=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:
*.wav=00;36:*.oga=00;36:*.opus=00;36:*.spx=00;36:*.xspf=00;36:', 'JAVA_HOME': '/usr/lib/jvm/java-7-openjdk-amd
64/jre/bin/java', 'LESSCLOSE': '/usr/bin/lesspipe %s %s', 'PWD': '/home/students'})
*----------------------------------*
/home/students
*----------------------------------*
/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
*----------------------------------*
Sample Solution-2:
Python Code:
import os
for data in os.environ:
print(data)
print('-'*15)
print(os.environ[data])
print('='*30)
Sample Output:
exit_code --------------- 0 ============================== node_version --------------- 8.11.3 ============================== versioning --------------- null ============================== version --------------- 0.0.0 ============================== unstable_restarts --------------- 0 ============================== restart_time --------------- 47 ============================== pm_id --------------- 0 ============================== created_at --------------- 1621962710172 ============================== axm_dynamic --------------- [object Object] ============================== axm_options --------------- [object Object] ============================== axm_monitor --------------- [object Object] ============================== axm_actions --------------- ============================== pm_uptime --------------- 1623108424625 ============================== status --------------- launching ============================== unique_id --------------- f981135a-143b-43bf-8ca1-906432f1f9e1 ============================== PM2_HOME --------------- /root/.pm2 ============================== PM2_INTERACTOR_PROCESSING --------------- true ============================== PM2_DISCRETE_MODE --------------- true ============================== PM2_PROGRAMMATIC --------------- true ============================== PYTHONPATH --------------- /trinket/python3 ============================== MPLBACKEND --------------- module://trinket_backend ============================== TERM --------------- xterm ============================== HOME --------------- /root ============================== LC_ALL --------------- en_US.UTF-8 ============================== LANGUAGE --------------- en_US:en ============================== LANG --------------- en_US.UTF-8 ============================== DEBIAN_FRONTEND --------------- teletype ============================== HOSTNAME --------------- 4735090b6baa ============================== PATH --------------- /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin ============================== NODE_APP_INSTANCE --------------- 0 ============================== vizion_running --------------- false ============================== km_link --------------- false ============================== pm_pid_path --------------- /root/.pm2/pids/shell-0.pid ============================== pm_err_log_path --------------- /dev/null ============================== pm_out_log_path --------------- /dev/null ============================== exec_mode --------------- fork_mode ============================== instances --------------- 1 ============================== exec_interpreter --------------- node ============================== pm_cwd --------------- /trinket-workdir ============================== pm_exec_path --------------- /trinket-workdir/server/python3/shell.js ============================== node_args --------------- ============================== name --------------- shell ============================== env --------------- [object Object] ============================== merge_logs --------------- true ============================== vizion --------------- true ============================== autorestart --------------- true ============================== instance_var --------------- NODE_APP_INSTANCE ============================== pmx --------------- true ============================== automation --------------- true ============================== treekill --------------- true ============================== username --------------- root ============================== windowsHide --------------- true ============================== kill_retry_time --------------- 100 ==============================
Flowchart:
Sample Solution-3:
Python Code:
import os
for item, value in os.environ.items():
print('{}: {}'.format(item, value))
Sample Output:
exit_code: 0 node_version: 8.11.3 versioning: null version: 0.0.0 unstable_restarts: 0 restart_time: 21 pm_id: 0 created_at: 1622456136302 axm_dynamic: [object Object] axm_options: [object Object] axm_monitor: [object Object] axm_actions: pm_uptime: 1623107594098 status: launching unique_id: 840ddab5-aa87-4cb5-ab04-16da1d9802f6 PM2_HOME: /root/.pm2 PM2_INTERACTOR_PROCESSING: true PM2_DISCRETE_MODE: true PM2_PROGRAMMATIC: true PYTHONPATH: /trinket/python3 MPLBACKEND: module://trinket_backend TERM: xterm HOME: /root LC_ALL: en_US.UTF-8 LANGUAGE: en_US:en LANG: en_US.UTF-8 DEBIAN_FRONTEND: teletype HOSTNAME: b0e45c20d4ca PATH: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin NODE_APP_INSTANCE: 0 vizion_running: false km_link: false pm_pid_path: /root/.pm2/pids/shell-0.pid pm_err_log_path: /dev/null pm_out_log_path: /dev/null exec_mode: fork_mode instances: 1 exec_interpreter: node pm_cwd: /trinket-workdir pm_exec_path: /trinket-workdir/server/python3/shell.js node_args: name: shell env: [object Object] merge_logs: true vizion: true autorestart: true instance_var: NODE_APP_INSTANCE pmx: true automation: true treekill: true username: root windowsHide: true kill_retry_time: 100
Flowchart:
Python Code Editor:
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Python: Tips of the Day
Find current directory and file's directory:
To get the full path to the directory a Python file is contained in, write this in that file:
import os dir_path = os.path.dirname(os.path.realpath(__file__))
(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)
To get the current working directory use
import os cwd = os.getcwd()
Documentation references for the modules, constants and functions used above:
- The os and os.path modules.
- The __file__ constant
- os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
- os.path.dirname(path) (returns "the directory name of pathname path")
- os.getcwd() (returns "a string representing the current working directory")
- os.chdir(path) ("change the current working directory to path")
Ref: https://bit.ly/3fy0R6m
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