I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?

--Jach

Jach Feng wrote:
> I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?

That depends on the command-line shell you're calling your script from.

In bash, you can include a newline in a quoted string:
../your_script 'step
'
(the closing quote is on the next line)

Or if you want to do it on a single line (or use other escape
sequences), you can use e.g.:
../your_script $'step\x0a'
(dollar sign before a single-quoted string which contains escape sequences)

--
Mark.

Mark Bourne 在 2022年12月20日 星期二凌晨4:49:13 [UTC+8] 的信中寫道：
> Jach Feng wrote:
> > I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?
> That depends on the command-line shell you're calling your script from.
>
> In bash, you can include a newline in a quoted string:
> ./your_script 'step
> '
> (the closing quote is on the next line)
>
> Or if you want to do it on a single line (or use other escape
> sequences), you can use e.g.:
> ./your_script $'step\x0a'
> (dollar sign before a single-quoted string which contains escape sequences)
>
> --
> Mark.
That's really good for Linux user! How about Windows?

On 12/19/2022 9:24 PM, Jach Feng wrote:
> Mark Bourne 在 2022年12月20日 星期二凌晨4:49:13 [UTC+8] 的信中寫道：
>> Jach Feng wrote:
>>> I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?
>> That depends on the command-line shell you're calling your script from.
>>
>> In bash, you can include a newline in a quoted string:
>> ./your_script 'step
>> '
>> (the closing quote is on the next line)
>>
>> Or if you want to do it on a single line (or use other escape
>> sequences), you can use e.g.:
>> ./your_script $'step\x0a'
>> (dollar sign before a single-quoted string which contains escape sequences)
>>
>> --
>> Mark.
> That's really good for Linux user! How about Windows?

One way is to process the argument after it gets into Python rather than
before. How hard that will be depends on how general you need the
argument to be. For your actual example, the argument comes into Python
as if it were

arg1 = r"step\x0A" # or "step\\x0a"

You can see if there is an "\\x":

pos = arg1.find('\\x') # 4

Replace or use a regex to replace it:

arg1_fixed = arg1.replace('\\x0A', '\n')

Naturally, if "\\x0A" is only a special case and other combinations are
possible, you will need to figure out what you need and do some more
complicated processing.

On 12/19/22, Jach Feng <jfong@ms4.hinet.net> wrote:
>
> That's really good for Linux user! How about Windows?

In CMD, typing the "^" escape character at the end of a line ignores
the newline and prompts for "more" input. If you press enter again,
you'll get another "more" prompt in which you can write the rest of
the command line. Command-line arguments are separated by spaces, so
you have to start the next line with a space if you want it to be a
new argument. Also, "^" is a literal character when it's in a
double-quoted string, which requires careful use of quotes. For
example:

C:\>py -c "import sys; print(sys.orig_argv[3:])" spam^
More?
More? eggs^
More?
More? " and spam"
['spam\n', 'eggs\n and spam']

The above is easier in PowerShell, which supports entering multiline
strings without having to escape the newline. The second-level prompt
is ">> ". For example:

> py -c "import sys; print(sys.orig_argv[3:])" spam"
>> " eggs"
>> and spam"
['spam\n', 'eggs\n and spam']

Thomas Passin 在 2022年12月20日 星期二上午11:36:41 [UTC+8] 的信中寫道：
> On 12/19/2022 9:24 PM, Jach Feng wrote:
> > Mark Bourne 在 2022年12月20日 星期二凌晨4:49:13 [UTC+8] 的信中寫道：
> >> Jach Feng wrote:
> >>> I have a script using the argparse module. I want to enter the string "step\x0A" as one of its positional arguments. I expect this string has a length of 5, but it gives 8. Obviously the escape character didn't function correctly. How to do it?
> >> That depends on the command-line shell you're calling your script from..
> >>
> >> In bash, you can include a newline in a quoted string:
> >> ./your_script 'step
> >> '
> >> (the closing quote is on the next line)
> >>
> >> Or if you want to do it on a single line (or use other escape
> >> sequences), you can use e.g.:
> >> ./your_script $'step\x0a'
> >> (dollar sign before a single-quoted string which contains escape sequences)
> >>
> >> --
> >> Mark.
> > That's really good for Linux user! How about Windows?
> One way is to process the argument after it gets into Python rather than
> before. How hard that will be depends on how general you need the
> argument to be. For your actual example, the argument comes into Python
> as if it were
>
> arg1 = r"step\x0A" # or "step\\x0a"
>
> You can see if there is an "\\x":
>
> pos = arg1.find('\\x') # 4
>
> Replace or use a regex to replace it:
>
> arg1_fixed = arg1.replace('\\x0A', '\n')
>
> Naturally, if "\\x0A" is only a special case and other combinations are
> possible, you will need to figure out what you need and do some more
> complicated processing.
That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)

ery...@gmail.com 在 2022年12月20日 星期二中午12:35:52 [UTC+8] 的信中寫道：
> On 12/19/22, Jach Feng <jf...@ms4.hinet.net> wrote:
> >
> > That's really good for Linux user! How about Windows?
> In CMD, typing the "^" escape character at the end of a line ignores
> the newline and prompts for "more" input. If you press enter again,
> you'll get another "more" prompt in which you can write the rest of
> the command line. Command-line arguments are separated by spaces, so
> you have to start the next line with a space if you want it to be a
> new argument. Also, "^" is a literal character when it's in a
> double-quoted string, which requires careful use of quotes. For
> example:
>
> C:\>py -c "import sys; print(sys.orig_argv[3:])" spam^
> More?
> More? eggs^
> More?
> More? " and spam"
> ['spam\n', 'eggs\n and spam']
>
> The above is easier in PowerShell, which supports entering multiline
> strings without having to escape the newline. The second-level prompt
> is ">> ". For example:
>
> > py -c "import sys; print(sys.orig_argv[3:])" spam"
> >> " eggs"
> >> and spam"
> ['spam\n', 'eggs\n and spam']
Thanks for the information. No idea Windows CMD can take such a trick to enter "\n" :-)

On Wed, 21 Dec 2022 at 15:28, Jach Feng <jfong@ms4.hinet.net> wrote:
> That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)

Technically, Windows DOES have a shell similar to bash. It's called
bash. :) The trouble is, most people use cmd.exe instead.

ChrisA

Chris Angelico 在 2022年12月21日 星期三下午1:02:01 [UTC+8] 的信中寫道：
> On Wed, 21 Dec 2022 at 15:28, Jach Feng <jf...@ms4.hinet.net> wrote:
> > That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)
> Technically, Windows DOES have a shell similar to bash. It's called
> bash. :) The trouble is, most people use cmd.exe instead.
>
> ChrisA
Really? Where? I can't find it in my Windows 8.1

On Thu, 22 Dec 2022 at 03:11, Jach Feng <jfong@ms4.hinet.net> wrote:
>
> Chris Angelico 在 2022年12月21日 星期三下午1:02:01 [UTC+8] 的信中寫道：
> > On Wed, 21 Dec 2022 at 15:28, Jach Feng <jf...@ms4.hinet.net> wrote:
> > > That's what I am taking this path under Windows now, the ultimate solution before Windows has shell similar to bash:-)
> > Technically, Windows DOES have a shell similar to bash. It's called
> > bash. :) The trouble is, most people use cmd.exe instead.
> >
> > ChrisA
> Really? Where? I can't find it in my Windows 8.1

Ah, I didn't mean "ships with"; bash for Windows is very much
available, but you'd have to go fetch it. Try the Windows app store
first, and if not, a quick web search will find it. Or install Git for
Windows, which comes with bash.

ChrisA