On 12/18/2011 10:43 PM, Peter Otten wrote:
nukeymusic wrote:
On 17 dec, 12:20, "Günther Dietrich"<gd.use...@spamfence.net> wrote:
nukeymusic<nukeymu...@gmail.com> wrote:
I'm trying to calculate the difference in seconds between two
[...]
import datetime
date1 = datetime.datetime.strptime("Dec-13-09:47:12",
"%b-%d-%H:%M:%S") date2 =
datetime.datetime.strptime("Dec-13-09:47:39", "%b-%d-%H:%M:%S") delta
= date2 - date1 delta_seconds = (delta.days * 60 * 60 * 24) +
delta.seconds + ((delta.microseconds + 500000) / 1000000)
For very big time differences you should consider to use the Decimal
arithmetics (standard module Decimal) instead of integer arithmetics
for the last line.
If you are sure, that you don't use fractional seconds, you can omit
the part with 'delta.microseconds'.
Best regards,
Günther
That can very much Günther, this helped me a lot further, I'm only
struggling with one more problem to finish my first python-program.
Could you
tell me why I can't write to the outputfile as I do in the code
below:?
#!/usr/bin/python
#version 16/12/2011
#Example of testfile
#Dec-13-09:46:45 21.4 +4.76442190E-01 8.135530E-06 1.553691E+00
#Dec-13-09:47:12 21.4 +4.76439120E-01 8.135839E-06 1.553726E+00
#Dec-13-09:47:39 21.4 +4.76427260E-01 8.136261E-06 1.553853E+00
import datetime
f = open('testfile','r')
g = open('outputfile','w')
#get line 1 from input file:
line1=f.readline()
#get first element in line 1:
date1=line1.rsplit()[0]
#convert first element tot structured date time
struct_date1=datetime.datetime.strptime(date1, "%b-%d-%H:%M:%S")
for line in f:
temp=line.rsplit()
delta=datetime.datetime.strptime(temp[0], "%b-%d-%H:%M:%S")-
datetime.datetime.strptime(date1, "%b-%d-%H:%M:%S")
delta_seconds = (delta.days * 60 * 60 * 24) + delta.seconds +
((delta.microseconds + 500000) / 1000000)
temp[0]=delta_seconds
#the following line is wrong, but I don't know how to fix it:
g.write(temp)
#Close files
f.close()
g.close()
The write() method only accepts strings; you have to convert the temp list
to a string before passing it on. The minimal change:
for line in f:
temp = line.rsplit()
delta = (datetime.datetime.strptime(temp[0], "%b-%d-%H:%M:%S")
-datetime.datetime.strptime(date1, "%b-%d-%H:%M:%S"))
delta_seconds = ((delta.days * 60 * 60 * 24) + delta.seconds
+ ((delta.microseconds + 500000) / 1000000))
temp[0] = str(delta_seconds)
g.write(" ".join(temp) + "\n")
Other observations:
- you are repeating calculations in the loop that you can do (and did)
outside.
- use four-space indent for better readability
- there's no need to use rsplit(); use split()
After a few other modifications:
import datetime
def parse_line(line):
date, rest = line.split(None, 1)
date = datetime.datetime.strptime(date, "%b-%d-%H:%M:%S")
return date, rest
with open('testfile','r') as f:
with open('outputfile','w') as g:
first_date, first_rest = parse_line(next(f))
for line in f:
cur_date, rest = parse_line(line)
delta = cur_date - first_date
delta_seconds = ((delta.days * 60 * 60 * 24) + delta.seconds
+ ((delta.microseconds + 500000) / 1000000))
g.write("%s %s" % (delta_seconds, rest))
minor improvement, you can do:
with open('testfile','r') as f, open('outputfile','w') as g:
...
instead of the nested with-block.
Also, you can use `delta.total_seconds()` instead of `delta_seconds =
((delta.days * 60 * 60 * 24) + delta.seconds + ((delta.microseconds +
500000) / 1000000))`
Therefore (untested):
import datetime
def parse_line(line):
date, rest = line.split(None, 1)
date = datetime.datetime.strptime(date, "%b-%d-%H:%M:%S")
return date, rest
with open('testfile','r') as f, open('outputfile','w') as g:
first_date, first_rest = parse_line(next(f))
for line in f:
cur_date, rest = parse_line(line)
delta = cur_date - first_date
g.write("%s %s" % (int(round(delta.total_seconds())), rest))
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