{"id":9419,"date":"2021-05-01T16:34:02","date_gmt":"2021-05-01T14:34:02","guid":{"rendered":"https:\/\/pythonprogramming.altervista.org\/?p=9419"},"modified":"2021-05-01T16:34:03","modified_gmt":"2021-05-01T14:34:03","slug":"how-to-solve-problems-with-python-and-regex","status":"publish","type":"post","link":"https:\/\/pythonprogramming.altervista.org\/how-to-solve-problems-with-python-and-regex\/","title":{"rendered":"How to solve problems with Python and regex"},"content":{"rendered":"\n

Let’s see how can we solve a problem <\/strong>automatically thanks to python <\/strong>getting the data from a text and making also the computer to find the solution for you, using the modile re for regex (tecnique to extract data from strings).<\/p>\n\n\n\n

\"\"<\/a><\/figure>\n\n\n\n

We will get a Break even point problem for example. Let’s see how to do it, step by step.<\/p>\n\n\n\n

Find all numbers in a text (\\d+)<\/h2>\n\n\n\n
\"\"<\/a><\/figure>\n\n\n\n
import re\n\n\ntmp = '''\nFind q\nwith:\n- p = 10 \u20ac\n- cv = 5 \u20ac\n\nCF = 3000 \u20ac\n\nsolution = \u20ac\u20ac\u20ac\n'''\n\ndata = re.findall(r\"\\d+\", tmp)\nprint(data)<\/pre>\n\n\n\n
The output<\/p>\n\n\n\n
\"\"<\/a>
Find all the numbers with \\d+<\/figcaption><\/figure>\n\n\n\n
A nice way to use the example above with the f string, notice that with the = symbol you can easily get what the value is related to.<\/p>\n\n\n\n
import re\n\n\ntmp = '''\nFind q\nwith:\n- p = 10 \u20ac\n- cv = 5 \u20ac\n\nCF = 3000 \u20ac\n\nsolution = \u20ac\u20ac\u20ac\n'''\n\ndata = re.findall(r\"\\d+\", tmp)\np, cv, CF = data\nprint(f\"{p=}\\n{cv=}\\n{CF=}\")<\/pre>\n\n\n\n
output<\/p>\n\n\n\n
\"\"<\/a><\/figure>\n\n\n\n
And you can also use the data to find a solution. In this case you got the fixed costs (CF) and the price and cost of the variable costs, so that you can find the break even point, that is the amount of sellings that make an enterprice to recover all the costs.<\/p>\n\n\n\n
p, cv, CF = [int(x) for x in data]\nprint(f\"{p=}\\n{cv=}\\n{CF=}\")\n\nsolution = CF \/ (p -cv)\nprint(solution)\nprint(\"This is the number of products you have to sell so that the revenues are equal to the costs.\")<\/pre>\n\n\n\n
The output would be this<\/p>\n\n\n\n
\"\"<\/a><\/figure>\n\n\n\n
Let’s make the exercise customizable<\/h2>\n\n\n\n
import re\n\ndef ex1(p=10, cv=5, CF=3000, sol=0):\n\t''' solve a bep problem '''\n\ttmp = f'''Find q with:\n\t- p = {p} \u20ac\n\t- cv = {cv} \u20ac\n\t- CF = {CF} \u20ac\n\tsolution = \u20ac\u20ac\u20ac\n\t'''\n\tpattern = r\"(\\d+(?:\\.\\d+)?)\"\n\tdata = re.findall(pattern, tmp)\n\tprint(data)\n\tp, cv, CF = [float(x) for x in data]\n\tprint(f\"{p=}\\n{cv=}\\n{CF=}\")\n\tsolution = int(CF \/ (p -cv))\n\t# print the solution if you pass sol=1\n\tif sol:\n\t\ttmp = tmp.replace(\"\u20ac\u20ac\u20ac\", str(solution))\n\tprint(tmp)\n\nex1()<\/pre>\n\n\n\n
If we call the ex1() function without arguments, the results will be the same, but if we give the function some arguments like this:<\/p>\n\n\n\n
ex1(p=12, cv=8.5, CF=100000, sol=1)<\/p>\n\n\n\n
\"\"<\/a><\/figure>\n\n\n\n
You can now put more call to the function with different data as argument for different solutions.<\/p>\n\n\n\n
Making random exercises for students with solution<\/h2>\n\n\n\n
This is to make random exercises. Let’s start<\/p>\n\n\n\n
import re\nimport random\n\n\ndef ex1(p=10, cv=5, CF=3000, sol=0):\n\t''' solve a bep problem '''\n\ttmp = f'''Trova il BEP sapendo che:\n\t- p = {p} \u20ac\n\t- cv = {cv} \u20ac\n\t- CF = {CF} \u20ac\n\tsolution = \u20ac\u20ac\u20ac\n\t'''\n\tpattern = r\"(\\d+(?:\\.\\d+)?)\"\n\tdata = p, cv, CF = re.findall(pattern, tmp)\n\t# print(f\"{p=} {cv=} {CF=}\")\n\tp, cv, CF = [float(x) for x in data]\n\t# print(f\"{p=} \u20ac\\n{cv=} \u20ac\\n{CF=} \u20ac\")\n\tsolution = int(CF \/ (p -cv))\n\t# print the solution if you pass sol=1\n\tif sol:\n\t\ttmp = tmp.replace(\"\u20ac\u20ac\u20ac\", str(solution))\n\tprint(tmp)\n\ndef randomize(number):\n\tfor r in range(number):\n\t\tp = random.randint(10, 20)\n\t\tcv = random.randint(p-10, p-5)\n\t\tCF = random.randrange(\n\t\t\t(p-cv)*random.randrange(1000, 2000, 100),\n\t\t\t(p-cv)*random.randrange(4000, 20000, 100),\n\t\t\t100\n\t\t\t)\n\t\tex1(p, cv, CF, sol=1)\n\n# ex1()\n# ex1(p=12, cv=8.5, CF=100000, sol=1)\nrandomize(3)<\/pre>\n\n\n\n
Output<\/p>\n\n\n\n
\"\"<\/a><\/figure>\n\n\n\n
Transform it in a quiz<\/h2>\n\n\n\n
import re\nimport random\n\n\ndef ex1(p=10, cv=5, CF=3000, sol=0, quiz=0):\n\t''' solve a bep problem '''\n\ttmp = f'''Trova il BEP sapendo che:\n\t- p = {p} \u20ac\n\t- cv = {cv} \u20ac\n\t- CF = {CF} \u20ac\n\t                [sol: ...........]\n\t'''\n\tpattern = r\"(\\d+(?:\\.\\d+)?)\"\n\tdata = p, cv, CF = re.findall(pattern, tmp)\n\t# print(f\"{p=} {cv=} {CF=}\")\n\tp, cv, CF = [float(x) for x in data]\n\t# print(f\"{p=} \u20ac\\n{cv=} \u20ac\\n{CF=} \u20ac\")\n\tsolution = int(CF \/ (p -cv))\n\t# print the solution if you pass sol=1\n\tif quiz:\n\t\tprint(tmp)\n\t\task(solution)\n\telse:\n\t\tif sol:\n\t\t\ttmp = tmp.replace(\"sol: ...........\", \"Soluzione: \" + str(solution))\n\t\t\tprint(tmp)\n\t\telse:\n\t\t\tprint(tmp)\n\ndef randomize(number=0, quiz=0, sol=0):\n\tfor r in range(number):\n\t\tp = random.randint(10, 20)\n\t\tcv = random.randint(p-10, p-5)\n\t\tCF = random.randrange(\n\t\t\t(p-cv)*random.randrange(1000, 2000, 100),\n\t\t\t(p-cv)*random.randrange(4000, 20000, 100),\n\t\t\t100\n\t\t\t)\n\t\tex1(p, cv, CF, sol, quiz)\n\ndef ask(solution):\n\tyousol = input(\"Sol:\")\n\tif yousol == str(solution):\n\t\tprint(\"Good job!\")\n\telse:\n\t\tprint(\"No, it's wrong\")\n\t\tprint(f\"{solution=}\\n\")\n# ex1()\n# ex1(p=12, cv=8.5, CF=100000, sol=1)\nrandomize(3, quiz=0, sol=0)<\/pre>\n\n\n\n
Let’s make it simple<\/h2>\n\n\n\n
We do not need the re module anymore.<\/p>\n\n\n\n
import random\n\n\ndef ex1(p=10, cv=5, CF=3000, sol=0, quiz=0):\n\t''' solve a bep problem '''\n\n\ttmp = f'''Trova il BEP sapendo che:\n\t- p = {p} \u20ac\n\t- cv = {cv} \u20ac\n\t- CF = {CF} \u20ac\n\t                [sol: ...........]\n\t                '''\n\n\tsolution = int(CF \/ (p -cv))\n\t# print the solution if you pass sol=1\n\tif quiz:\n\t\tprint(tmp)\n\t\task(solution)\n\telse:\n\t\tif sol:\n\t\t\ttmp = tmp.replace(\"sol: ...........\", \"Soluzione: \" + str(solution))\n\t\t\tprint(tmp)\n\t\telse:\n\t\t\tprint(tmp)\n\ndef randomize(number=0, quiz=0, sol=0):\n\tfor r in range(number):\n\t\tp = random.randint(10, 20)\n\t\tcv = random.randint(p-10, p-5)\n\t\tCF = random.randrange(\n\t\t\t(p-cv)*random.randrange(1000, 2000, 100),\n\t\t\t(p-cv)*random.randrange(4000, 20000, 100),\n\t\t\t100\n\t\t\t)\n\t\tex1(p, cv, CF, sol, quiz)\n\ndef ask(solution):\n\tyousol = input(\"Sol:\")\n\tif yousol == str(solution):\n\t\tprint(\"Good job!\\n\")\n\telse:\n\t\tprint(\"No, it's wrong\")\n\t\tprint(f\"{solution=}\\n\")\n# ex1()\n# ex1(sol=1)\n# ex1(p=12, cv=8.5, CF=100000, sol=1)\nrandomize(3, quiz=1, sol=1)<\/pre>\n\n\n\n
How you can use it<\/p>\n\n\n\n
ex1()<\/td>the example with default data<\/td><\/tr>
ex1(sol=1)<\/td>same as above, but with the solution<\/td><\/tr>
ex1(p=12, cv=10, CF=2000, sol=1)<\/td>custom exercise
p = price
cv = variable costs
CF = fixed costs
sol=1 # to show the solution<\/td><\/tr>
randomize(3, sol=1)<\/td>creates 3 random exercizes with solution<\/td><\/tr>
 randomize(3, quiz=1) <\/td>Makes a quiz with 3 problems to solve<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
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