Re: How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?
On 1/22/23 11:44, Stefan Ram wrote: > Jach Feng writes: >> e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2" > > Well, it's a nice exercise! But I only made it work for the > specific example given. I have not tested whether it always > works. Haha. Yes a nice exercise, but has nothing to do with the original question which is how to convince argparse to accept a string like that without thinking it's a switch. Many unix utilities treat "--" as a special argument that turns off argument parsing for the rest of the command line. Maybe argparse follows this convention too; I don't know. But if it did you'd do: infix2postfix.py -- "-4^2+5.3*abs(-2-1)/2" -- https://mail.python.org/mailman/listinfo/python-list
Re: How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?
On 21Jan2023 19:11, Jach Feng wrote:
Fail on command line,
e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2"
usage: infix2postfix.py [-h] [infix]
infix2postfix.py: error: unrecognized arguments: -4^2+5.3*abs(-2-1)/2
The usual convention for having "nonoption" arguments beginning with a
dash/minus is to explicitly _end_ the option arguments, eg:
py infix2postfix.py -- "-4^2+5.3*abs(-2-1)/2"
That "--" indicates the end of the options, and that what follows should
not be treated as an option. _However_, it requires support in the
script parsing the options. I'm pretty sure argparse gives that support
for free, as does getopt and probably any others implementing "normal
UNIXish options".
SO try adding a "--" argument and see how it behaves.
Also fail in REPL,
e:\Works\Python>py
Python 3.8.8 (tags/v3.8.8:024d805, Feb 19 2021, 13:08:11) [MSC v.1928 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
import argparse
parser = argparse.ArgumentParser(description='Convert infix notation to
postfix')
parser.parse_args("-4^2+5.3*abs(-2-1)/2")
usage: [-h]
: error: unrecognized arguments: - 4 ^ 2 + 5 . 3 * a b s ( - 2 - 1 ) / 2
This is a different error. `parse_args()` expects a list of arguments,
not a single argument. So it has iterated over what you gave it, which
produces a series of single character strings which it has taken to be
individual arguments. Try this:
parser.parse_args(["-4^2+5.3*abs(-2-1)/2"])
and of course:
parser.parse_args(["--", "-4^2+5.3*abs(-2-1)/2"])
You can see this behaviour of strings as:
print(list("abc"))
or:
for s in "abc":
print("s =", repr(s))
Cheers,
Cameron Simpson
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Re: How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?
Argparse is for parsing command line arguments and options.
If you just want to evaluate an Python expression, use eval( )
Your string isn’t valid Python due to order of operations, but
-(4^2)+5.3*abs(-2-1)/2 is.
From: Python-list on
behalf of Jach Feng
Date: Sunday, January 22, 2023 at 11:24 AM
To: python-list@python.org
Subject: Re: How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?
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Thomas Passin 在 2023年1月22日 星期日下午1:30:39 [UTC+8] 的信中寫道：
> On 1/21/2023 10:11 PM, Jach Feng wrote:
> > Fail on command line,
> >
> > e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2"
> > usage: infix2postfix.py [-h] [infix]
> > infix2postfix.py: error: unrecognized arguments: -4^2+5.3*abs(-2-1)/2
> >
> > Also fail in REPL,
> >
> > e:\Works\Python>py
> > Python 3.8.8 (tags/v3.8.8:024d805, Feb 19 2021, 13:08:11) [MSC v.1928 32
> > bit (Intel)] on win32
> > Type "help", "copyright", "credits" or "license" for more information.
> import argparse
> parser = argparse.ArgumentParser(description='Convert infix notation to
> postfix')
> parser.parse_args("-4^2+5.3*abs(-2-1)/2")
> > usage: [-h]
> > : error: unrecognized arguments: - 4 ^ 2 + 5 . 3 * a b s ( - 2 - 1 ) / 2
> >
> > Just can't figure out where is wrong!?
> It just doesn't work like that. If you download the package, there is
> only one python file, __init__.py. This file contains one class. It
> has a demo at the end, commented out. If you uncomment those lines and
> run the file, you get a result printed.
>
> These remarks are based on downloading the link for the source
> distribution from Pypi
> (https://urldefense.com/v3/__https://pypi.org/project/infix2postfix/__;!!Cn_UX_p3!gqKmYLlyUndAzxmJsqCB429izQ-2-KMbpGP2eVzp_iDKtbgQXfrCu21UBvepq-F9EXb4SJwP516MHeUFMBtW$
> ). When I installed it with
> pip, nothing seems to have gotten installed although pip went through
> the motions and claimed it was. So I just downloaded the source package.
>
> The test expression is "-(a*b)+(c+d)-(a+b+c+d)". The test output for
> this is "ab*-cd++ab+c+d+-".
>
> If you substitute your expression, the result is
>
> abs1-2-*2/3.5+2^4-
>
> This may or may not be correct. I'm not sure but I think it's as
> intended except for reversing "3.5". But maybe that's right, I'm not
> too sure. Notice that this file is in its first release, version 0.0.1
> - the metadata that says it's 'Development Status :: 5 -
> Production/Stable' seems to be bogus. So it may very well be buggy.
>
> At any rate, if you want to use it in a program that can accept
> arguments, you will have to write that part yourself. And the
> expression you feed it would need to be a single string, meaning it has
> to be quoted on the command line as you have done (although on Windows
> you should be using double quotes instead of single quotes).
>
> As for argparse, it isn't doing what you want because you haven't told
> it what to do with the arguments.
Sorry to cause confusion here. I don't know there is a Pypi project with the
same name infix2postfix.py:-(
Nevertheless, Is there anyway to make parse_args works?
>>> parser.parse_args("-4^2+5.3*abs(-2-1)/2")
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Re: tree representation of Python data
On 1/21/2023 10:03 AM, Dino wrote:
I have a question that is a bit of a shot in the dark. I have this nice
bash utility installed:
$ tree -d unit/
unit/
├── mocks
├── plugins
│ ├── ast
│ ├── editor
│ ├── editor-autosuggest
│ ├── editor-metadata
│ ├── json-schema-validator
│ │ └── test-documents
│ └── validate-semantic
│ ├── 2and3
│ ├── bugs
│ └── oas3
└── standalone
└── topbar-insert
I just thought that it would be great if there was a Python utility that
visualized a similar graph for nested data structures.
Of course I am aware of indent (json.dumps()) and pprint, and they are
OK options for my need. It's just that the compact, improved
visualization would be nice to have. Not so nice that I would go out of
my way to build, but nice enough to use an exising package.
It's not clear to me whether you want to display JSON structures or
Python objects. However, Python dictionaries are so similar to JSON
structures that a dictionary example should be pretty close.
This can actually be a tricky problem because for complicated nesting,
it's not that easy to work out how to display the elements. The
examples posted in this thread so far have been somewhat obscured by the
use of leader lines, etc, so that it's a little hard to discern the
simple core of the algorithm.
Below I include code that displays each leaf element on its own indented
line, can only display keys and simple leaf values, and does not
construct leader lines so as to keep the code easy to read. In this
form it can only display Python dictionaries but could be modified for
JSON without too much work.
"""Display nested objects as an indented list."""
INDENT = ' ' * 3
DICT = {'a': {'aa':'AA', 'ab':'AB'},
'b': {'ba': {'baa': 'BAA', 'bab': 'BAB'},
'bb':'BB'},
'c': ['CA', 'CB'],
'd': 'D' }
SIMPLE_TYPES = (int, float, str, bytes)
def unroll(obj, indent = ''):
if isinstance(obj, dict):
unroll_dict(obj, indent)
else:
"""unroll other kinds of objects (not implemented)."""
print(indent, 'Can only unroll nested dictionaries')
def unroll_dict(dct, indent = ''):
"""Unroll a dictionary whose values can be either simple or
nested.
"""
for k, v in dct.items():
g.es(indent, k)
new_indent = indent + INDENT
if type(v) in SIMPLE_TYPES:
print(new_indent, v)
else:
unroll(v, new_indent)
# print(f'{new_indent}{v}')
unroll(DICT)
Output:
a
aa
AA
ab
AB
b
ba
baa
BAA
bab
BAB
bb
BB
c
Can only unroll nested dictionaries
d
D
If you change the last else block, you can make use of the object's
internal representation (not for JSON, of course). Change the block to
read:
# unroll(v, new_indent)
print(f'{new_indent}{v}')
This change gives the following output:
a
{'aa': 'AA', 'ab': 'AB'}
b
{'ba': {'baa': 'BAA', 'bab': 'BAB'}, 'bb': 'BB'}
c
['CA', 'CB']
d
D
In practice, I would collect the text fragments into a list instead of
printing them, then print the joined list at the end.
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Re: How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?
On 1/22/2023 10:45 AM, Peter J. Holzer wrote: Notice that this file is in its first release, version 0.0.1 - the metadata that says it's 'Development Status :: 5 - Production/Stable' seems to be bogus. So it may very well be buggy. It is at least too incomplete to be useful. It handles only single letters as operands and treats everything else (except parentheses) as an operator, handling only +, -, *, / and ^ correctly (actually, ^ is typically right associative, so that's arguably wrong, too). This script is basically useless without some documentation on the intended inputs and outputs, and how to invoke it. The documentation could (in the minimal case) have been included in docstrings and comments within the script. As it is, the script seems tantalizing but unusable. Please document your work, even if it's just for yourself! -- https://mail.python.org/mailman/listinfo/python-list
Re: How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?
Jach Feng wrote:
Fail on command line,
e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2"
usage: infix2postfix.py [-h] [infix]
infix2postfix.py: error: unrecognized arguments: -4^2+5.3*abs(-2-1)/2
Also fail in REPL,
e:\Works\Python>py
Python 3.8.8 (tags/v3.8.8:024d805, Feb 19 2021, 13:08:11) [MSC v.1928 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
import argparse
parser = argparse.ArgumentParser(description='Convert infix notation to
postfix')
parser.parse_args("-4^2+5.3*abs(-2-1)/2")
usage: [-h]
: error: unrecognized arguments: - 4 ^ 2 + 5 . 3 * a b s ( - 2 - 1 ) / 2
Just can't figure out where is wrong!?
First, you need to add an argument to the parser, so that it expects an
argument:
>>> parser.add_argument("expression")
Secondly, `parse_args` expects a list of arguments. By passing a
string, it interprets each character as a separate argument (since
iterating over a string yields each character in turn). Here, I
intentionally leave off the initial hyphen because that's the next problem:
>>> parser.parse_args(["4^2+5.3*abs(-2-1)/2"])
Namespace(expression='4^2+5.3*abs(-2-1)/2')
Thirdly, an initial hyphen indicates an optional argument so, for
example if you pass "-l" it will expect a "-l" argument to be defined as
one of the valid options, and also complain that you haven't specified
the required expression:
>>> parser.parse_args(["-4^2+5.3*abs(-2-1)/2"])
usage: [-h] expression
: error: the following arguments are required: expression
If you need to pass a value starting with a "-" there are a couple of
options...
Perhaps it would be acceptable to represent it as "0-...":
>>> parser.parse_args(["0-4^2+5.3*abs(-2-1)/2"])
Namespace(expression='0-4^2+5.3*abs(-2-1)/2')
While mathematically equivalent, that might have different meaning for
whatever you're trying to do. Alternatively, a double hyphen indicates
that there are no more options and that anything else is positional
arguments even if they begin with a hyphen:
>>> parser.parse_args(["--", "-4^2+5.3*abs(-2-1)/2"])
Namespace(expression='-4^2+5.3*abs(-2-1)/2')
You wouldn't usually explicitly pass a list of arguments to `parse_args`
like that, but it can be useful for testing and experimentation.
Usually, you'd call `parse_args()` without any arguments, and it would
parse the arguments passed on the command-line when calling your script.
e.g. you'd call (from a Windows command prompt / Linux shell / etc.):
> ./convert_infix.py -- '-4^2+5.3*abs(-2-1)/2'
(it's probably a good idea to quote the expression, in case it includes
any characters which would be interpreted specially by the shell - e.g.
"*" without quotes usually expands to all matching files in the current
directory)
--
Mark.
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Re: How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?
Thomas Passin 在 2023年1月22日 星期日下午1:30:39 [UTC+8] 的信中寫道：
> On 1/21/2023 10:11 PM, Jach Feng wrote:
> > Fail on command line,
> >
> > e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2"
> > usage: infix2postfix.py [-h] [infix]
> > infix2postfix.py: error: unrecognized arguments: -4^2+5.3*abs(-2-1)/2
> >
> > Also fail in REPL,
> >
> > e:\Works\Python>py
> > Python 3.8.8 (tags/v3.8.8:024d805, Feb 19 2021, 13:08:11) [MSC v.1928 32
> > bit (Intel)] on win32
> > Type "help", "copyright", "credits" or "license" for more information.
> import argparse
> parser = argparse.ArgumentParser(description='Convert infix notation to
> postfix')
> parser.parse_args("-4^2+5.3*abs(-2-1)/2")
> > usage: [-h]
> > : error: unrecognized arguments: - 4 ^ 2 + 5 . 3 * a b s ( - 2 - 1 ) / 2
> >
> > Just can't figure out where is wrong!?
> It just doesn't work like that. If you download the package, there is
> only one python file, __init__.py. This file contains one class. It
> has a demo at the end, commented out. If you uncomment those lines and
> run the file, you get a result printed.
>
> These remarks are based on downloading the link for the source
> distribution from Pypi
> (https://pypi.org/project/infix2postfix/). When I installed it with
> pip, nothing seems to have gotten installed although pip went through
> the motions and claimed it was. So I just downloaded the source package.
>
> The test expression is "-(a*b)+(c+d)-(a+b+c+d)". The test output for
> this is "ab*-cd++ab+c+d+-".
>
> If you substitute your expression, the result is
>
> abs1-2-*2/3.5+2^4-
>
> This may or may not be correct. I'm not sure but I think it's as
> intended except for reversing "3.5". But maybe that's right, I'm not
> too sure. Notice that this file is in its first release, version 0.0.1
> - the metadata that says it's 'Development Status :: 5 -
> Production/Stable' seems to be bogus. So it may very well be buggy.
>
> At any rate, if you want to use it in a program that can accept
> arguments, you will have to write that part yourself. And the
> expression you feed it would need to be a single string, meaning it has
> to be quoted on the command line as you have done (although on Windows
> you should be using double quotes instead of single quotes).
>
> As for argparse, it isn't doing what you want because you haven't told
> it what to do with the arguments.
Sorry to cause confusion here. I don't know there is a Pypi project with the
same name infix2postfix.py:-(
Nevertheless, Is there anyway to make parse_args works?
>>> parser.parse_args("-4^2+5.3*abs(-2-1)/2")
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Re: How to make argparse accept "-4^2+5.3*abs(-2-1)/2" string argument?
On 2023-01-22 00:30:07 -0500, Thomas Passin wrote:
> On 1/21/2023 10:11 PM, Jach Feng wrote:
> > e:\Works\Python>py infix2postfix.py "-4^2+5.3*abs(-2-1)/2"
> > usage: infix2postfix.py [-h] [infix]
> > infix2postfix.py: error: unrecognized arguments: -4^2+5.3*abs(-2-1)/2
[...]
> > > > > import argparse
> > > > > parser = argparse.ArgumentParser(description='Convert infix notation
> > > > > to postfix')
> > > > > parser.parse_args("-4^2+5.3*abs(-2-1)/2")
> > usage: [-h]
> > : error: unrecognized arguments: - 4 ^ 2 + 5 . 3 * a b s ( - 2 - 1 ) / 2
> >
> > Just can't figure out where is wrong!?
>
> It just doesn't work like that.
[...]
> If you substitute your expression, the result is
>
> abs1-2-*2/3.5+2^4-
>
> This may or may not be correct. I'm not sure but I think it's as intended
> except for reversing "3.5". But maybe that's right, I'm not too sure.
It depends on the intended meaning. But I'm pretty sure that "5.3" is
supposed to be a floating point number and not (5 operatordot 3), so
it's wrong to split that apart. (Also it seems that the code treats
digits as operators, not operands?)
Also "abs(...)" is almost certainly intended to be a function call, so
it should be invoked after its parameters.
I think the correct output (using newlines as delimiters) would be:
-4
2
^
5.3
-2
1
-
abs
*
2
/
+
> Notice that this file is in its first release, version 0.0.1 - the metadata
> that says it's 'Development Status :: 5 - Production/Stable' seems to be
> bogus. So it may very well be buggy.
It is at least too incomplete to be useful. It handles only single
letters as operands and treats everything else (except parentheses) as an
operator, handling
only +, -, *, / and ^ correctly (actually, ^ is typically right
associative, so that's arguably wrong, too).
hp
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|_|_) ||
| | | h...@hjp.at |-- Charles Stross, "Creative writing
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