Python: How to add/subtract a number only to numeric characters in a string?

Question

Say for example, I have the following strings and an input 4.0, which represents seconds:

John Time Made 11:05:20 in 2010
5.001 Kelly #1
6.005 Josh #8

And would like the following result:

John Time Made 11:05:24 in 2010 #Input 4.0 is added to the seconds of 11:05:20
1.001 Kelly #1 #4.0 is subtracted from the first number 5.001 = 1.001
2.005 Josh #8 #4.0 is subtracted from the first number 5.001 = 2.005

How can I recognize the hours:minutes:seconds in the first line, and #.### in the rest to add/subtract the input number?

Thank you in advance and will accept/upvote answer

Answer 1

This solution should work if your complete data has the same format as this particular sample you provided. You should have the data in the input.txt file.

val_to_add = 4

with open('input.txt') as fin:
    # processing first line
    first_line = fin.readline().strip()
    splitted = first_line.split(' ')

    # get hour, minute, second corresponding to time (11:05:20)
    time_values = splitted[3].split(':')

    # seconds is the last element
    seconds = int(time_values[-1])

    # add the value
    new_seconds = seconds + val_to_add

    # doing simple math to avoid having values >= 60 for minute and second
    # this part probably can be solved with datetime or some other lib, but it's not that complex, so I did it in couple of lines
    seconds = new_seconds % 60 # if we get > 59 seconds we only put the modulo as second and the other part goes to minute
    new_minutes = int(time_values[1]) + new_seconds // 60 # if we have more than 60 s then here we'll add minutes produced by adding to the seconds
    minutes = new_minutes % 60 # similarly as for seconds
    hours = int(time_values[0]) + new_minutes // 60

    # here I convert again to string so we could easily apply join operation (operates only on strings) and additionaly add zero in front for 1 digit numbers
    time_values[0] = str(hours).rjust(2, '0')
    time_values[1] = str(minutes).rjust(2, '0')
    time_values[2] = str(seconds).rjust(2, '0')

    new_time_val = ':'.join(time_values)# join the values to follow the HH:MM:SS format
    splitted[3] = new_time_val# replace the old time with the new one (with the value added)
    first_line_modified = ' '.join(splitted)# just join the modified list

    print(first_line_modified)

    # processing othe lines
    for line in fin:
        # here we only get the first (0th) value and subtract the val_to_add and round to 3 digits the response (to avoid too many decimal places)
        stripped = line.strip()
        splitted = stripped.split(' ')
        splitted[0] = str(round(float(splitted[0]) - val_to_add, 3))
        modified_line = ' '.join(splitted)
        print(modified_line)

Answer 2

Although regex was discouraged in the comments, regex can be used to parse the time objects into datetime.time objects, perform the necessary calculations on them, then print them in the required format:

# datetime module for time calculations
import datetime
# regex module
import re

# seconds to add to time
myinp = 4

# List of data strings
# data = 'John Time Made 11:05:20 in 2010', '5.001 Kelly', '6.005 Josh'

with open('data.txt') as f:
    data = f.readlines()

new_data = []

#iterate through the list of data strings
for time in data:
    try:
        # First check for 'HH:MM:SS' time format in data string
        #   regex taken from this question: http://stackoverflow.com/questions/8318236/regex-pattern-for-hhmmss-time-string
        match = re.findall("([0-1]?\d|2[0-3]):([0-5]?\d):([0-5]?\d)", time)
        # this regex returns a list of tuples as strings "[('HH', 'MM', 'SS')]", 
        #   which we join back together with ':' (colon) separators 
        t = ':'.join(match[0])
        # create a Datetime object from indexing the first matched time in the list,
        #   taken from this answer http://stackoverflow.com/questions/100210/what-is-the-standard-way-to-add-n-seconds-to-datetime-time-in-python
        # May create an IndexError exception, which we catch in the `except` clause below
        orig = datetime.datetime(100,1,1,int(match[0][0]), int(match[0][1]), int(match[0][2]))
        # Add the number of seconds to the Datetime object,
        #   taken from this answer: http://stackoverflow.com/questions/656297/python-time-timedelta-equivalent
        newtime = (orig + datetime.timedelta(0, myinp)).time()
        # replace the time in the original data string with the newtime and print
        new_data.append(time.replace(t, str(newtime)))
    # catch an IndexError Exception, which we look for float-formatted seconds only
    except IndexError:
        # look for float-formatted seconds (s.xxx)      
        #   taken from this answer: http://stackoverflow.com/questions/4703390/how-to-extract-a-floating-number-from-a-string 
        match = re.findall("\d+\.\d+", time)
        # create a Datetime object from indexing the first matched time in the list,
        #   specifying only seconds, and microseconds, which we convert to milliseconds (micro*1000)
        orig = datetime.datetime(100,1,1,second=int(match[0].split('.')[0]),microsecond=int(match[0].split('.')[1])*1000)
        # Subtract the seconds from the Datetime object, similiar to the time addtion in the `try` clause above
        newtime = orig - datetime.timedelta(0, myinp)
        # format the newtime as `seconds` concatenated with the milliseconds converted from microseconds
        newtime_fmt = newtime.second + newtime.microsecond/1000000.
        # Get the seconds value (first value(index 0)) from splitting the original string at the `space` between the `seconds` and `name` strings 
        t = time.split(' ')[0]
        # replace the time in the original data string with the newtime and print
        new_data.append(time.replace(t , str(newtime_fmt)))


with open('new_data.txt', 'w') as nf:
    for newline in new_data:
        nf.write(newline)

new_data.txt file contents should read as:

John Time Made 11:05:24 in 2010
1.001 Kelly
2.005 Josh