Python argparse default value or specified value

Question

I would like to have a optional argument that will default to a value if only the flag is present with no value specified  but store a user-specified value instead of the default if the user specifies a value  Is there already an action available for this   An example   python script py --example   args example would equal a default value of 1 python script py --example 2   args example would equal a default value of 2   I can create an action  but wanted to see if there was an existing way to do this

User · Answer

The difference between   parser add argument  --debug   help  Debug   nargs      type int  const 1  default 7    and   parser add argument  --debug   help  Debug   nargs      type int  const 1    is thus   myscript py              debug is 7  from default  in the first case and  None  in the second  myscript py --debug      debug is 1 in each case  myscript py --debug 2    debug is 2 in each case

User · Answer

Actually  you only need to use the default argument to add argument as in this test py script   import argparse  if   name         main          parser   argparse ArgumentParser       parser add argument  --example   default 1      args   parser parse args       print args example      test py --example   1 test py --example 2   2   Details are here

User · Answer

import argparse parser   argparse ArgumentParser   parser add argument  --example   nargs      const 1  type int  args   parser parse args   print args        test py  Namespace example None    test py --example Namespace example 1    test py --example 2 Namespace example 2       nargs     means 0-or-1 arguments const 1 sets the default when there are 0 arguments type int converts the argument to int     If you want test py to set example to 1 even if no --example is specified  then include default 1  That is  with  parser add argument  --example   nargs      const 1  type int  default 1    then    test py  Namespace example 1

[python] Python argparse: default value or specified value

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