Argparse Required arguments listed under optional arguments

Question

I use the following simple code to parse some arguments  note that one of them is required  Unfortunately  when the user runs the script without providing the argument  the displayed usage help text does not indicate that there is a non-optional argument  which I find very confusing  How can I get python to indicate that an argument is not optional   Here is the code   import argparse if   name         main         parser   argparse ArgumentParser          description  Foo       parser add argument  -i   --input   help  Input file name   required True      parser add argument  -o   --output   help  Output file name   default  stdout       args   parser parse args       print   Input file   s    args input       print   Output file   s    args output     When running above code without providing the required argument  I get the following output   usage  foo py  -h  -i INPUT  -o OUTPUT   Foo  optional arguments      -h  --help            show this help message and exit     -i INPUT  --input INPUT                           Input file name     -o OUTPUT  --output OUTPUT                           Output file name

User · Answer

One more time  building off of  RalphyZ  This one doesn t break the exposed API   from argparse import ArgumentParser  SUPPRESS   Disable default help parser   ArgumentParser add help False  required   parser add argument group  required arguments   optional   parser add argument group  optional arguments      Add back help  optional add argument       -h        --help       action  help       default SUPPRESS      help  show this help message and exit    required add argument  --required arg   required True  optional add argument  --optional arg     Which will show the same as above and should survive future versions   usage  main py  -h   --required arg REQUIRED ARG              --optional arg OPTIONAL ARG   required arguments    --required arg REQUIRED ARG  optional arguments    -h  --help                    show this help message and exit   --optional arg OPTIONAL ARG

User · Answer

Since I prefer to list required arguments before optional  I hack around it via       parser   argparse ArgumentParser       parser  action groups pop       required   parser add argument group  required arguments       optional   parser add argument group  optional arguments       required add argument  --required arg   required True      optional add argument  --optional arg       return parser parse args     and this outputs   usage  main py  -h   --required arg REQUIRED ARG                  --optional arg OPTIONAL ARG   required arguments    --required arg REQUIRED ARG  optional arguments    --optional arg OPTIONAL ARG   I can live without  help  showing up in the optional arguments group

User · Answer

Parameters starting with - or -- are usually considered optional  All other parameters are positional parameters and as such required by design  like positional function arguments   It is possible to require optional arguments  but this is a bit against their design  Since they are still part of the non-positional arguments  they will still be listed under the confusing header    optional arguments    even if they are required  The missing square brackets in the usage part however show that they are indeed required   See also the documentation      In general  the argparse module assumes that flags like -f and --bar indicate optional arguments  which can always be omitted at the command line       Note  Required options are generally considered bad form because users expect options to be optional  and thus they should be avoided when possible    That being said  the headers    positional arguments    and    optional arguments    in the help are generated by two argument groups in which the arguments are automatically separated into  Now  you could    hack into it    and change the name of the optional ones  but a far more elegant solution would be to create another group for    required named arguments     or whatever you want to call them    parser   argparse ArgumentParser description  Foo   parser add argument  -o    --output   help  Output file name   default  stdout   requiredNamed   parser add argument group  required named arguments   requiredNamed add argument  -i    --input   help  Input file name   required True  parser parse args   -h        usage   -h   -o OUTPUT  -i INPUT  Foo  optional arguments    -h  --help            show this help message and exit   -o OUTPUT  --output OUTPUT                         Output file name  required named arguments    -i INPUT  --input INPUT                         Input file name

User · Answer

Building off of  Karl Rosaen  parser   argparse ArgumentParser   optional   parser  action groups pop     Edited this line required   parser add argument group  required arguments     remove this line  optional   parser    required add argument  --required arg   required True  optional add argument  --optional arg   parser  action groups append optional    added this line return parser parse args     and this outputs   usage  main py  -h   --required arg REQUIRED ARG              --optional arg OPTIONAL ARG   required arguments    --required arg REQUIRED ARG  optional arguments    -h  --help                    show this help message and exit   --optional arg OPTIONAL ARG

[python] Argparse: Required arguments listed under "optional arguments"?

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