Learn python argparse module download install and use

Learn python argparse module download install and use

The Argparse module in Python replaces the previous Optparse module and is often used to parse command-line arguments and options.

Position parameters:

Start with one of the most basic programs (it does not implement any realistic functionality):

Import Argparse
Parser = Argparse. Argumentparser ()
Parser.parse_args ()

Here is the result after the run:

$ python prog.py
$ python prog.py--help
usage:prog.py [-h]optional arguments:
-H,--help show this help message and exit$ python prog.py--verbose
usage:prog.py [-h]prog.py:error:unrecognized arguments:--verbose
$ Python prog.py foo
usage:prog.py [-h]prog.py:error:unrecognized Arguments:foo

Null when no arguments are added

"--help" was added to the command line on the second execution, and a friendly help message was obtained.

The--HELP option can also be abbreviated to-H, which is the only parameter that can be used without our setting, and any other parameter will be an error.



Example:

Import Argparse
Parser = Argparse. Argumentparser ()
Parser.add_argument ("echo")
args = Parser.parse_args ()
Print Args.echo

Operation Result:

$ python prog.py
usage:prog.py [-H] Echo
Prog.py:error:the following arguments is Required:echo
$ python prog.py--help
usage:prog.py [-H] Echo

Positional Arguments:echo

Optional arguments:
-H,--help show this help message and exit
$ Python prog.py foo
Foo

We added the Add_argument () method, which specifies which command-line arguments the program accepts. In this example, we define it as echo.

Now we need to specify an option when invoking the program.

The Parse_args () method actually returns some data from our command-line arguments, which in the example above is the Echo

Although the auto-generated help information is beautifully presented, it is still not possible to know exactly what it is doing based on the echo parameter. So we're going to make it a little more practical.

Import Argparse
Parser = Argparse. Argumentparser ()
Parser.add_argument ("echo", help= "echo the string,")
args = Parser.parse_args ()
Print Args.echo

Run again:

$ python prog.py-h
usage:prog.py [-H] Echo
Positional arguments:
echo echo the string

Optional arguments:
-H,--help show this help message and exit

Now add some more:

Import Argparse
Parser = Argparse. Argumentparser ()
Parser.add_argument ("Square", help= "display a square of a given number")
args = Parser.parse_args ()
Print args.square**2

Results:

$ python prog.py 4
Traceback (most recent):
File "prog.py", line 5, <module>
Print args.square**2
typeerror:unsupported operand type (s) for * * or POW (): ' str ' and ' int '

Error after operation. This is because by default Argparse takes the arguments we pass as string, so in this case we need to tell it that we are going to pass an integer-type argument.

Import Argparse
Parser = Argparse. Argumentparser ()
Parser.add_argument ("Square", help= "display a square of a given number", Type=int)
args = Parser.parse_args ()
Print args.square**2

Operation Result:

$ python prog.py 4
16
$ python prog.py Four
usage:prog.py [-h] Square
prog.py:error:argument square:invalid int value: ' Four '

Now, the program runs smoothly and can handle some of the wrong inputs.

Manuscripts: Diligent Learning qxkue.net

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Learn python argparse module download install and use