[PATCH] tbot_contrib/utils.py: convert a string into a dictionary via a pattern

[Heiko Schocher]

Hello Harald,

Am 05.05.2020 um 17:02 schrieb Harald Seiler:
> Hello Heiko,
> 
> On Mon, 2020-04-20 at 15:51 +0200, Heiko Schocher wrote:
>> introduce function string_to_dict(), which converts
>> a string into dictionary via a pattern.
> 
> Can you quickly explain where this helper is useful to you?  IMO the name
> string_to_dict() doesn't really hint at what it does.  If I can see this
> correctly, this is kind of a reverse string formatting.  So maybe
> match_format(), parse_format(), or unformat() would be more appropriate?

I used if for example to parse a output line of the latency
command:

output lines are from the follwoing format:

     # RTT|  00:00:01  (periodic user-mode task, 1000 us period, priority 99)
     # RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
     # RTD|     11.458|     16.702|     39.250|       0|     0|     11.458|     39.250

so if a line contains RTD I used the format:

     rtd_format = 'RTD\|{min}\|{avg}\|{max}\|{overrun}\|{msw}\|{best}\|{worst}'

and did:

     for l in ret:
         if 'RTD' in l["out"]:
             rtd_dict = string_to_dict(l["out"], rtd_format)


Ok, we can rename it to "parse_format" ?

But may there is some easier trick with python 3 ?

> 
>> Signed-off-by: Heiko Schocher <hs at denx.de>
>> ---
>>
>>   tbot_contrib/utils.py | 25 +++++++++++++++++++++++++
>>   1 file changed, 25 insertions(+)
>>
>> diff --git a/tbot_contrib/utils.py b/tbot_contrib/utils.py
>> index 8073f89..1afb65b 100644
>> --- a/tbot_contrib/utils.py
>> +++ b/tbot_contrib/utils.py
>> @@ -15,6 +15,7 @@
>>   # along with this program.  If not, see <https://www.gnu.org/licenses/>;;;.
>>   
>>   from tbot.machine import linux
>> +import re
>>   
>>   
>>   def check_systemd_services_running(lnx: linux.LinuxShell, services: list) -> None:
>> @@ -29,3 +30,27 @@ def check_systemd_services_running(lnx: linux.LinuxShell, services: list) -> Non
>>           ret = lnx.exec("systemctl", "status", s, "--no-pager")
>>           if ret[0] != 0:
>>               lnx.test("sudo", "systemctl", "start", s)
>> +
>> +
>> +def string_to_dict(string: str, pattern: str) -> dict:
> 
> Annotation for the return type needs to be typing.Dict[str, str].
> 
> Also, to keep consistent with the rest of Python (e.g. the `re` module),
> the arguments should be switched so that pattern comes first.

Ok, can clean this up...

>> +    """
>> +    convert a string into a dictionary via a pattern
>> +
>> +    example pattern:
>> +    'hello, my name is {name} and I am a {age} year old {what}'
>> +
>> +    string:
>> +    'hello, my name is dan and I am a 33 year old developer'
>> +
>> +    returned dict:
>> +    {'age': '33', 'name': 'dan', 'what': 'developer'}
>> +    from:
>> +    https://stackoverflow.com/questions/11844986/convert-or-unformat-a-string-to-variables-like-format-but-in-reverse-in-p
>> +    """
>> +    regex = re.sub(r"{(.+?)}", r"(?P<_\1>.+)", pattern)
> 
> The match-pattern used here, `(?P<_group>.+)` matches greedy.  This means
> for your above example that the following string
> 
>      hello, my name is dan and I am a 33 year old developer and I am a 33 year old developer
> 
> will yield
> 
>      {'name': 'dan and I am a 33 year old developer', 'age': '33',
>       'what': 'developer'}
> 
> Not sure if this is a problem though.  It could be changed by using
> `(?P<_group>.+?)` instead if non-greedy behavior is more desirable.

Yes, I change this.

Thanks!

bye,
Heiko
> 
>> +    match = re.search(regex, string)
>> +    assert match is not None, f"The pattern {regex!r} was not found!"
>> +    values = list(match.groups())
>> +    keys = re.findall(r"{(.+?)}", pattern)
>> +    _dict = dict(zip(keys, values))
>> +    return _dict

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-52   Fax: +49-8142-66989-80   Email: hs at denx.de