A list where each attribute is a string of words, and splitting each attribute into a new list where-CodePudding

I'm a beginner python programmer and new to this forum website. I've searched around and haven't been able to find what I've been looking for, so I came here.

I have a function that calculates the percent error between two values given from user input, writes that value to a file in the string: 'Trial x % error = y', where x is the trial number and y equals the float value of the percent error. Every time this function is run, it adds a new line to the file and writes, 'Trial (x 1) % error = y', this way it is easy to track your trials. The function then turns each line in the file into an attribute of a list, and prints to the console the last item in that list.

To fix this, I decided a way to do this was to: split each attribute in the list (which is a string of words) where a space is, and save each word in a line to its own list. This way I could index the second attribute in the new list and save it to the value x, add 1 to it, and that would be the new value of x.

def percentError():
    x = 1
    #defining formula
    error = str(100 * (measured - accepted) / (accepted))
    #opening % Error.txt
    errorTxt =  open('% Error.txt', 'a')
    #writing in file
    errorTxt.write('Trial '   str(x)   ' % error = '   error   '%')
    #new line
    errorTxt.write('\n')
    #close file
    errorTxt.close()
    #open file again
    errorTxt = open('% Error.txt', 'r')
    #read from and print what is read
    trial = []
    trialNum = []
    for line in errorTxt:
      trial.append(line.strip())
    print(trial[-1])
    for attribute in trial[-1]:
       z = trial.split(' ')
       trialNum.append(z)
    x = trialNum[1]
    #file close
    errorTxt.close()

There's code above the comment (#defining formula) that has user inputs for the variables of measured and accepted, I left it out for readability.

This gives me the error - AttributeError: 'list' has no attribute 'split'

Anyone know how to fix my problem? The goal is to have x only increase by 1 from the highest trial number in the file.

CodePudding user response：

You can write a simple tokenizer with the re module. Maybe like this:

import re
def simple_tokenize(text):
    return re.sub(r"\W", " ", text).split()

Then you can turn your list of text strings into a list of list of words like:

data_in = [
    "To be, or not to be, that is the question:",
    "Whether ’tis nobler in the mind to suffer",
    "The slings and arrows of outrageous fortune,",
    "Or to take arms against a sea of troubles,",
    "And by opposing end them?"
]

data_out = [simple_tokenize(line) for line in data_in]

print(data_out)

Giving you:

[
    ['To', 'be', 'or', 'not', 'to', 'be', 'that', 'is', 'the', 'question'],
    ['Whether', 'tis', 'nobler', 'in', 'the', 'mind', 'to', 'suffer'],
    ['The', 'slings', 'and', 'arrows', 'of', 'outrageous', 'fortune'],
    ['Or', 'to', 'take', 'arms', 'against', 'a', 'sea', 'of', 'troubles'],
    ['And', 'by', 'opposing', 'end', 'them']
]

Looking at your specific code and your description of what you want to do in the end, I think there is a lot of it you can remove and a bunch of the work/splitting/parsing you are doing is redundant.

If you want to:

Calculate the percent error between two values given from user input.
writes that value to a file in the string: 'Trial x % error = y'
the function to determine trial based on prior data

You might try:

def percentError(measured, accepted):
    error = 100 * (measured - accepted) / (accepted)

    with open('percent_error.txt', 'a ') as error_file:
        error_file.seek(0)

        try:
            last_line = error_file.readlines()[-1]
            last_trial_number = int(last_line.split()[1])
        except (ValueError, IndexError):
            last_trial_number = 0

        last_line = f"Trial {last_trial_number   1} % error = {error}%"
        error_file.write(f"{last_line}\n")

    print(last_line)

percentError(10,8)
percentError(10,9)
percentError(10,7)

user_measured = int(input("enter measured: ")) ## note this is brittle and will error if the user enters bad data
user_accepted = int(input("enter accepted: ")) ## note this is brittle and will error if the user enters bad data
percentError(user_measured, user_accepted)

Should show you:

Trial 1 % error = 25.0%
Trial 2 % error = 11.11111111111111%
Trial 3 % error = 42.857142857142854%

and a 4th trial based on your user input.

then it will generate a file "percent_error.txt" with the same results