I want to update an existing file.txt in Python, which has two columns, one for days, and one for time, so that it will sum up a new time in another column on the same file.
Sunday 07:00
Monday 07:35
Tuesday 05:35
Wednesday 06:45
Thursday 08:40
For example, adding 30 minutes:
Sunday 07:00 07:30
Monday 07:35 08:05
Tuesday 05:35 06:05
Wednesday 06:45 07:15
Thursday 08:40 09:10
The datetime module is very helpful for this. It lets you create time objects and timedelta objects which can be added together by simply using the + operator. So, to add thirty minutes to 08:30:25:
>>> from datetime import datetime, timedelta
>>> d = datetime.strptime("08:30:25", "%I:%M:%S") + timedelta(minutes=30)
>>> d.strftime("%I:%M:%S")
'09:00:25'
In [139]: d='Sunday 07:00'
In [140]: b=d.split()
In [141]: b
Out[141]: ['Sunday', '07:00']
In [142]: (datetime.datetime.strptime(b[1], '%H:%M') + datetime.timedelta(minutes=30)).strftime('%H:%M')
Out[142]: '07:30'
from datetime import datetime, timedelta
f=open("testcase","r") #open the file
pairs = [l.split() for l in f.readlines()] #get [day,time] pairs
f.close()
#this long line creates a list of [day,time1,time2] using list comprehensions
#you can change it a bit to change the output format.
data = ["%s%s%s\n" % (p[0].ljust(12),p[1].ljust(8),
(datetime.strptime(p[1],"%H:%M") + timedelta(minutes=30)).strftime("%H:%M"))
for p in pairs]
#reopen the file for writing and store the new data.
f = open("testcase","w")
f.writelines(data)
f.close();
