[issue41087] Argparse int / float default

[Vedran Čačić]

Vedran Čačić  added the comment:

Python _is_ strongly typed. As soon as you try to use that 0.005 as an index 
into a list or something else that requires an int, you'll get a TypeError. 
Strong typing is not the same as static typing. It is a common misconception.

And common sense is always common to something. For humans it is common sense 
that we have two eyes, but it's not common to spiders. As I said, what is 
common sense in statically typed languages is not necessarily common to Python.

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[issue41087] Argparse int / float default

[Serhiy Storchaka]

Change by Serhiy Storchaka :


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resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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[issue41087] Argparse int / float default

[Bryan]

Bryan  added the comment:

So you agree, Python lacks common sense...

On Wed, 24 Jun 2020 at 03:32, Vedran Čačić  wrote:

>
> Vedran Čačić  added the comment:
>
> Yes, it is common sense in statically typed languages. Python is not
> statically typed. Many other things are also "common sense" in various
> paradigms, which doesn't mean they should also be in Python.
>
> --
> nosy: +veky
>
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[issue41087] Argparse int / float default

[Vedran Čačić]

Vedran Čačić  added the comment:

Yes, it is common sense in statically typed languages. Python is not statically 
typed. Many other things are also "common sense" in various paradigms, which 
doesn't mean they should also be in Python.

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nosy: +veky

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[issue41087] Argparse int / float default

[Bryan]

Bryan  added the comment:

This sort of ambiguity is why I like strongly typed languages and languages
where timtoady is not seen often.

I can guarantee you, that if argparse was implemented in Pascal (and copt
most probably has been), that if type was specified and a default given,
that the default would have to adhere to that type. It is just programming
common sense

On Wed, 24 Jun 2020 02:20 paul j3,  wrote:

>
> paul j3  added the comment:
>
> No, parameters like `type` let the developer control what his users
> provides.  Violating that produces a runtime error, and exit.
>
> But in general argparse does not try to control values that the developer
> uses.  There's plenty of time during development to catch error such as
> this - if they are errors at all.
>
> 'type' does not 'declare' what the attribute will be.  It is a function
> that is applied to the input string, and converts that to something or
> other, or raises a TypeError.  It is used only if there is a string value
> to work on, either from the user, or a string default.
>
> This is not a bug, so should be closed.
>
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[issue41087] Argparse int / float default

[paul j3]

paul j3  added the comment:

No, parameters like `type` let the developer control what his users provides.  
Violating that produces a runtime error, and exit.

But in general argparse does not try to control values that the developer uses. 
 There's plenty of time during development to catch error such as this - if 
they are errors at all.  

'type' does not 'declare' what the attribute will be.  It is a function that is 
applied to the input string, and converts that to something or other, or raises 
a TypeError.  It is used only if there is a string value to work on, either 
from the user, or a string default.  

This is not a bug, so should be closed.

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[issue41087] Argparse int / float default

[Bryan]

Bryan  added the comment:

Maybe so,

But, the issue is, if it trips up a user when they try to use the option,
it should trip up the dev when the default is used...

On Tue, 23 Jun 2020 18:47 Karthikeyan Singaravelan, 
wrote:

>
> Karthikeyan Singaravelan  added the comment:
>
> There is a documentation note on type casting along with an example
> similar to the report
> https://docs.python.org/3.8/library/argparse.html#default
>
> > If the default value is a string, the parser parses the value as if it
> were a command-line argument. In particular, the parser applies any type
> conversion argument, if provided, before setting the attribute on the
> Namespace return value. Otherwise, the parser uses the value as is:
>
> --
> nosy: +paul.j3, rhettinger, xtreak
> type:  -> behavior
>
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[issue41087] Argparse int / float default

[Karthikeyan Singaravelan]

Karthikeyan Singaravelan  added the comment:

There is a documentation note on type casting along with an example similar to 
the report https://docs.python.org/3.8/library/argparse.html#default

> If the default value is a string, the parser parses the value as if it were a 
> command-line argument. In particular, the parser applies any type conversion 
> argument, if provided, before setting the attribute on the Namespace return 
> value. Otherwise, the parser uses the value as is:

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nosy: +paul.j3, rhettinger, xtreak
type:  -> behavior

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[issue41087] Argparse int / float default

[Bryan]

New submission from Bryan :

parser.add_argument('-e', '--Edge', type = int, default = 0.005, metavar = 
'Edge')

Runs fine. Script uses default of 0.005 even when int specified.

But if user tries to change, not an int

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messages: 372143
nosy: Bryan
priority: normal
severity: normal
status: open
title: Argparse int / float default
versions: Python 3.8

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