how do I extract a specific value from a string in python?-CodePudding

I have a string with this structure:

[519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992],12,160p30

I need to find the value after ], that here is 12. I need this value to use in a for loop. how can I do this?

CodePudding user response：

If you have same structure of data you can use regexp to extract part of strings you need to use. In described case it can be done like this:

import re


test_string = '[519.1743772241992, 519.1743772241992, 519.1743772241992, '\
                '519.1743772241992, 519.1743772241992, 519.1743772241992],'\
                '12,160p30'

pattern = r'(^\[. \]),([0-9] ),(. $)'

result = re.search(pattern, test_string)

print(result.group(1))
# [519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992]

print(result.group(2))
# 12

print(result.group(3))
# 160p30

CodePudding user response：

If all you want is at the right end of your string, you can use rsplit instead of split

s = "[519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992],12,160p30"
val = s.rsplit(",", 2)[1]  # val get value "12" from s

rsplit will split your string from the right starting at the separator "," a maximum of 2 times. As you want the second to last value of your string, use indexing to get the desired value.

CodePudding user response：

string = "[519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992, 519.1743772241992],1,160p30"
i = string.rfind("],")   2
value = int(string[i : string.find(",", i)])
print(value)

CodePudding user response：

yourString = ''
stringToFindLength = 2
keyCharacter = ']'
shortString = ''
for i in yourString:
   if i == keyCharacter:
      shortString = yourString[i:i stringToFindLength]

This is called string indexing, and it's a pretty big part of python, I think everything I put here would check out okay, but just in case, you should read up on string indexing:

https://www.digitalocean.com/community/tutorials/how-to-index-and-slice-strings-in-python-3

https://www.w3schools.com/python/ref_string_index.asp

there's also the index() function

yourString = ''
searchString = '12'
shortString = yourString.index(searchString)