regex, 7 lines clear solution for Write Quadratic Equation by kdim - python coding challenges

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regex, 7 lines solution in Clear category for Write Quadratic Equation by kdim

from re import sub
def quadr_equation(data) -> str:
    (a, x1), x2 = (data[:2]), data[-1]
    quad = f'{a}*x**2+{-a * x1 - a * x2}*x+{a * x1 * x2} = 0'       # get str like - "-1*x**2+-1*x+0 = 0"
    quad = sub(r'(\+|\-)0\*x(\*\*2)?|\+0', r'', quad)               # remove zeros - "0*x"->""   , "+0"->""
    quad = sub(r'(\+|\-)?1\*|\+(\-)', r'\1\2', quad)                # remove ones  - "1*x"->"x"  , "+-"->"-"
    return sub(r'(.)(\+|\-)', r'\1 \2 ', quad)                      # add spaces   -   "-"->" - ",  "+"->" + "

Sept. 16, 2022

Comments:

juestr on Sept. 20, 2022, 1:42 p.m.
That's a rather creative solution.

kdim on Sept. 20, 2022, 3:27 p.m.
It should be moved to the 3rd party category. Reread the rules.

hbczmxy on Nov. 3, 2022, 2:11 a.m.
Your solution is really creative! Especially the use of Regular Expression in your solution! But I can't fully understand your solution? Can you give me some more explanations? Especially the fifth to seventh sentences. <pre class='brush: python'># how did it works? # "|\+0". The END of RegEx, I don't understand it very well! quad = sub(r'(\+|\-)0\*x(\*\*2)?|\+0', r'', quad) # remove zeros - "0*x"->"" , "+0"->"" quad = sub(r'(\+|\-)?1\*|\+(\-)', r'\1\2', quad) # remove ones - "1*x"->"x" , "+-"->"-" </pre> If you can, I'd be very grateful!

kdim on Nov. 7, 2022, 3:15 p.m.
<a href="https://docs.python.org/3/library/re.html">https://docs.python.org/3/library/re.html</a> `re.sub(pattern, repl, string, count=0, flags=0)` Return the string obtained by replacing the leftmost non-overlapping occurrences of pattern in string by the replacement repl. If the pattern isn’t found, string is returned unchanged. repl can be a string or a function; if it is a string, any backslash escapes in it are processed. For pattern you can use `r'abc|def'` its any of `'abc'` or `'def'`. In our case we need to replace any of `'0x2'`, `'+0x'`, `'+0'` to empty string. And pattern may `r'0*x**2|+0*x|+0'`, `'+'` and `'*'` must be escaped with `'\'`. Or same optimization - `r'+?0*?x?*?*?2?'` Or grouping - `r'+?0(*x)?(**2)?'`, `r'+?0(*x(**2)?)?'` Try <a href="https://regex101.com">https://regex101.com</a> for practice, there is both `python` and `sub`.

kdim on Nov. 7, 2022, 3:24 p.m.
<pre class='brush: python'>from re import sub def quadr_equation(data) -> str: (a, x1), x2 = (data[:2]), data[-1] quad = f'{a}*x**2+{-a * x1 - a * x2}*x+{a * x1 * x2} = 0' quad = sub(r'\+0\*x|\+0|1\*', r'', quad) return sub(r'(.)\+?(\+|-)', r'\1 \2 ', quad) </pre> @hbczmxy thanks for your question. I found a couple of bugs and optimizations. Solution fit in 6 lines.

kdim on Nov. 7, 2022, 3:28 p.m.
<a href="https://docs.python.org/3/library/re.html">https://docs.python.org/3/library/re.html</a> `re.sub(pattern, repl, string, count=0, flags=0)` Return the string obtained by replacing the leftmost non-overlapping occurrences of pattern in string by the replacement repl. If the pattern isn’t found, string is returned unchanged. repl can be a string or a function; if it is a string, any backslash escapes in it are processed. For pattern you can use `r'abc|def'` its any of `'abc'` or `'def'`. In our case we need to replace any of `'0x2'`, `'+0x'`, `'+0'` to empty string. And pattern may `r'0*x**2|+0*x|+0'`, `'+'` and `'*'` must be escaped with `'\'`. Or same optimization - `r'+?0*?x?*?*?2?'` Or grouping - `r'+?0(*x)?(**2)?'`, `r'+?0(*x(**2)?)?'` Try <a href="https://regex101.com">https://regex101.com</a> for practice, there is both `python` and `sub`.

kdim on Nov. 7, 2022, 3:48 p.m.
Its more interesting pattern `r'(.)+?(+|-)'` with replace `r'\1 \2 '`. For string `'2x2+-x-5 = 0'` pattern have two match: First match `'(2)+(-)'` and replace `'2 - '`. Second mtch `'(x)(-)'` and replace `'x - '`. And result - `'2x2 - x - 5 = 0'`

H0r4c3 on Jan. 21, 2023, 8:01 p.m.
A very good lesson in regex!

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