Python - print section of file using line number

e.g. Print the section of input file 'input.txt' between line number 22 and 89.

Using python enumerate function sequence numbers:

for i,line in enumerate(open("file.txt")):
    if i >= 21 and i < 89 :
        print line,

And if you want to write the section to a new file say '/tmp/fileA'

fp = open("/tmp/fileA","w")
for i,line in enumerate(open("file.txt")):
    if i >= 21 and i < 89 :
        fp.write(line)

Another approach:

print(''.join(open('file.txt', 'r').readlines()[21:89])),

And if you wish to write the section to a new file say '/tmp/fileB'

fp = open("/tmp/fileB","w")
fp.write(''.join(open('file.txt', 'r').readlines()[21:89])),

Read about python enumerate function here and below is a small example using python enumerate function:

>>> for i, student in enumerate(['Alex', 'Ryan', 'Deb']):
...     print i, student
...
0 Alex
1 Ryan
2 Deb
>>>

Also find my other post on Extracting section of a file using line numbers applying awk, sed, Perl, vi editor and UNIX/Linux head and tail command techniques.

Python - Adding numbers in a list

Lets see some of ways in python to add the numbers present in a list.

Suppose:

>>> numlist = [10,20,5,30]
>>> numlist
[10, 20, 5, 30]
>>> print sum(numlist)
65

Using python built in function 'reduce'

>>> numlist
[10, 20, 5, 30]
>>> def add(x, y): return x + y
...
>>> sum = reduce(add, numlist)
>>> sum
65

Enhancing the above using python 'lambda' function

>>> numlist
[10, 20, 5, 30]
>>> reduce(lambda b,a: a+b, numlist)
65
>>>

Or using python for loop:

>>> numlist
[10, 20, 5, 30]
>>> sum = 0
>>> for i in numlist:
...     sum += i
...
>>> sum
65
>>>

Python - time difference between dates

Required:

Find the time difference between two dates (of following format) in seconds and in hh:mm:ss format.

e.g.

date1='Oct/09/2009 10:58:01' and
date2='Oct/10/2009 12:17:10'

find the difference between date1 and date2 in seconds(i.e. 91149 seconds) and later convert it to hh:mm:ss format (i.e. 25:19:09).

The complete python program:

import sys,time,string,getopt

def usage():
    print "Usage: adbtimediff.py -f <fromTime> -t <toTime> \n"
    sys.exit(2)


def parse_args():
    global fromTime,toTime
    fromTime = toTime = ""

    try:
        opts, args = getopt.getopt(sys.argv[1:], "f:t:", ["fromtime", "totime"])
    except getopt.GetoptError:
        print "Invalid arguments, exiting"
        sys.exit(2)

    for arg, val in opts:
        if  arg in ("-f","--fromtime"):
            fromTime = val
        elif arg in ("-t","--totime"):
            toTime = val

    if fromTime == toTime == "" :
        usage()

def compute_time(time1):
    t = time1.split(':')
    return time.mktime(time.strptime(":".join(t[0:len(t)]),"%b/%d/%Y %H:%M:%S"))

def subtract(list):
    return list[1] - list[0]

def time_convert(secs):
    secs = int(secs)
    mins = secs // 60
    hrs = mins // 60
    return "%02d:%02d:%02d" % (hrs, mins % 60, secs % 60)

def main():
    parse_args()
    print "Fromtime : " + str(fromTime) + '\n' + "Totime : " + str(toTime)
    timelist = [ fromTime, toTime ]
    s = map(compute_time,timelist)
    d = subtract(s)
    print "diff in seconds : " + str(d)
    f = str(d).split('.')
    final = time_convert(f[0])
    print "Total difference in required format : " + str(final)

main()

Executing the above script:

$ python timediff.py -f 'Oct/09/2009  10:58:01' -t 'Oct/10/2009  12:17:10'

Output:

Fromtime : Oct/09/2009  10:58:01
Totime : Oct/10/2009  12:17:10
diff in seconds : 91149.0
Total difference in required format : 25:19:09

Related concepts and posts:

- Convert seconds to hh:mm:ss format using python
- Python time.mktime
- Python time.strftime
- Python map
- Python getopt

Python - seconds to hh-mm-ss conversion

Solution1: Using python 'time' module strftime function.

 
Python 2.5.2 (r252:60911, Jul 22 2009, 15:35:03)
[GCC 4.2.4 (Ubuntu 4.2.4-1ubuntu3)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import time
>>> time.strftime('%H:%M:%S', time.gmtime(7302))
'02:01:42'
>>> time.strftime('%H:%M:%S', time.gmtime(86399))
'23:59:59'
>>> time.strftime('%H:%M:%S', time.gmtime(86405))
'00:00:05'

So as seen above this solution works only for num seconds < 1 day (86400 seconds)

Solution2: Using python datetime module, timedelta object.

>>> import datetime
>>> x = datetime.timedelta(seconds=7302)
>>> str(x)
'2:01:42'
>>> x = datetime.timedelta(seconds=86399)
>>> str(x)
'23:59:59'
>>> x = datetime.timedelta(seconds=86405)
>>> str(x)
'1 day, 0:00:05'

Solution3: Using normal division in python

import sys

secs = int(sys.argv[1])
mins = secs // 60
hrs = mins // 60

#hh:mm:ss
print "%02d:%02d:%02d" % (hrs, mins % 60, secs % 60)

#mm:ss
print "%02d:%02d" % (mins, secs % 60)

Executing it:

$ python timeconv.py 7302
02:01:42
121:42

$ python timeconv.py 86399
23:59:59
1439:59

$ python timeconv.py 86405
24:00:05
1440:05

Print line above pattern in python

Input file: 'data.txt' contains results of a set of students in the following format.

$ cat data.txt
id:502
Result:Pass
id:909
Result:Fail
id:503
Result:Pass
id:501
Result:Pass
id:802
Result:Fail

Required:
Print the Ids of the students who have passed the exam.

The python program:

fp = open("passedids.txt","w")
data = open("data.txt").readlines()
for i in range(len(data)):
        if data[i].startswith("Result:Pass"):
                fp.write(data[i-1].split(":")[1])

Output:

$ cat passedids.txt
502
503
501

Python - delete lines between two pattern

Input file:

$ cat input.txt
test1
test2
test3
BEGIN
test4
test5
test6
END
test7
test8
test9
BEGIN
test10
test11
END
test12

Required:
From the above file delete the lines which are between a BEGIN-END block and print rest of the lines.

The python script deleteline.py:

flag = 1
linelist = open("input.txt").readlines()
for line in linelist:
    if line.startswith("BEGIN"):
        flag = 0
    if line.startswith("END"):
        flag = 1
    if flag and not line.startswith("END"):
       print line,

Executing it:

$ python deleteline.py
test1
test2
test3
test7
test8
test9
test12

Now if we need to print the lines which are between a BEGIN-END block.
Here is a modification of the above scirpt.

flag = 1
linelist = open("input.txt").readlines()
for line in linelist:
    if line.startswith("BEGIN"):
        flag = 0
    if line.startswith("END"):
        flag = 1
    if not flag and not line.startswith("BEGIN"):
       print line,

Executing it:

$ python printline.py
test4
test5
test6
test10
test11

Related post:

- Lookup file operation using python