Develop Reference

Python perform actions only at certain locations in text file

I have a text file which contains the data like this
AA 331
line1 ...
line2 ...
% information here
AA 332
line1 ...
line2 ...
line3 ...
%information here
AA 1021
line1 ...
line2 ...
% information here
AA 1022
line1 ...
% information here
AA 1023
line1 ...
line2 ...
% information here
I want to perform action only for "informations" that comes after smallest integer that is after line "AA 331"and line "AA 1021" and not after lines "AA 332" , "AA 1022" and "AA 1023" .
P.s This is just a sample data of large file
The below code i try to parse the text file and get the integers which are after "AA" in a list "list1" and in second function i group them to get minimal value in "list2". This will return integers like [331,1021,...]. So i thought of extracting lines which comes after "AA 331" and perform action but i d'nt know how to proceed.
from itertools import groupby
def getlineindex(textfile):
with open(textfile) as infile:
list1 = []
for line in infile :
if line.startswith("AA"):
intid = line[3:]
list1.append(intid)
return list1
def minimalinteger(list1):
list2 = []
for k,v in groupby(list1,key=lambda x: x//10):
minimalint = min(v)
list2.append(minimalint)
return list2
list2 contains the smallest integers which comes after "AA" [331,1021,..]

You can use something like:
import re
matcher = re.compile("AA ([\d]+)")
already_was = []
good_block = False
with open(filename) as f:
for line in f:
m = matcher.match(line)
if m:
v = int(m.groups(0)) / 10
else:
v = None
if m and v not in already_was:
good_block = True
already_was.append(m)
if m and v in already_was:
good_block = False
if not m and good_block:
do_action()
These code works only if first value in group is minimal one.

Okay, here's my solution. At a high level, I go line by line, watching for AA lines to know when I've found the start/end of a data block, and watch what I call the run number to know whether or not we should process the next block. Then, I have a subroutine that handles any given block, basically reading off all relevant lines and processing them if needed. That subroutine is what watches for the next AA line in order to know when it's done.
import re
runIdRegex = re.compile(r'AA (\d+)')
def processFile(fileHandle):
lastNumber = None # Last run number, necessary so we know if there's been a gap or if we're in a new block of ten.
line = fileHandle.next()
while line is not None: # None is being used as a special value indicating we've hit the end of the file.
processData = False
match = runIdRegex.match(line)
if match:
runNumber = int(match.group(1))
if lastNumber == None:
# Startup/first iteration
processData = True
elif runNumber - lastNumber == 1:
# Continuation, see if the tenths are the same.
lastNumberTens = lastNumber / 10
runNumberTens = runNumber / 10
if lastNumberTens != runNumberTens:
processData = True
else:
processData = True
# Always remember where we were.
lastNumber = runNumber
# And grab and process data.
line = dataBlock(fileHandle, process=processData)
else:
try:
line = fileHandle.next()
except StopIteration:
line = None
def dataBlock(fileHandle, process=False):
runData = []
try:
line = fileHandle.next()
match = runIdRegex.match(line)
while not match:
runData.append(line)
line = fileHandle.next()
match = runIdRegex.match(line)
except StopIteration:
# Hit end of file
line = None
if process:
# Data processing call here
# processData(runData)
pass
# Return line so we don't lose it!
return line
Some notes for you. First, I'm in agreement with Jimilian that you should use a regular expression to match AA lines.
Second, the logic we talked about with regard to when we should process data is in processFile. Specifically these lines:
processData = False
match = runIdRegex.match(line)
if match:
runNumber = int(match.group(1))
if lastNumber == None:
# Startup/first iteration
processData = True
elif runNumber - lastNumber == 1:
# Continuation, see if the tenths are the same.
lastNumberTens = lastNumber / 10
runNumberTens = runNumber / 10
if lastNumberTens != runNumberTens:
processData = True
else:
processData = True
I assume we don't want to process data, then identify when we do. Logically speaking, you can do the inverse of this and assume you want to process data, then identify when you don't. Next, we need to store the last run's value in order to know whether or not we need to process this run's data. (and watch out for that first run edge case) We know we want to process data when the sequence is broken (the difference between two runs is greater than 1), which is handled by the else statement. We also know that we want to process data when the sequence increments the digit in the tens place, which is handled by my integer divide by 10.
Third, watch out for that return data from dataBlock. If you don't do that, you're going to lose the AA line that caused dataBlock to stop iterating, and processFile needs that line in order to know whether the next data block should be processed.
Last, I've opted to use fileHandle.next() and exception handling to identify when I get to the end of the file. But don't think this is the only way. :)
Let me know in comments if you have any questions.

How do you make tables with previously stored strings?

So the question basically gives me 19 DNA sequences and wants me to makea basic text table. The first column has to be the sequence ID, the second column the length of the sequence, the third is the number of "A"'s, 4th is "G"'s, 5th is "C", 6th is "T", 7th is %GC, 8th is whether or not it has "TGA" in the sequence. Then I get all these values and write a table to "dna_stats.txt"
Here is my code:
fh = open("dna.fasta","r")
Acount = 0
Ccount = 0
Gcount = 0
Tcount = 0
seq=0
alllines = fh.readlines()
for line in alllines:
if line.startswith(">"):
seq+=1
continue
Acount+=line.count("A")
Ccount+=line.count("C")
Gcount+=line.count("G")
Tcount+=line.count("T")
genomeSize=Acount+Gcount+Ccount+Tcount
percentGC=(Gcount+Ccount)*100.00/genomeSize
print "sequence", seq
print "Length of Sequence",len(line)
print Acount,Ccount,Gcount,Tcount
print "Percent of GC","%.2f"%(percentGC)
if "TGA" in line:
print "Yes"
else:
print "No"
fh2 = open("dna_stats.txt","w")
for line in alllines:
splitlines = line.split()
lenstr=str(len(line))
seqstr = str(seq)
fh2.write(seqstr+"\t"+lenstr+"\n")
I found that you have to convert the variables into strings. I have all of the values calculated correctly when I print them out in the terminal. However, I keep getting only 19 for the first column, when it should go 1,2,3,4,5,etc. to represent all of the sequences. I tried it with the other variables and it just got the total amounts of the whole file. I started trying to make the table but have not finished it.
So my biggest issue is that I don't know how to get the values for the variables for each specific line.
I am new to python and programming in general so any tips or tricks or anything at all will really help.
I am using python version 2.7

Well, your biggest issue:
for line in alllines: #1
...
fh2 = open("dna_stats.txt","w")
for line in alllines: #2
....
Indentation matters. This says "for every line (#1), open a file and then loop over every line again(#2)..."
De-indent those things.

This puts the info in a dictionary as you go and allows for DNA sequences to go over multiple lines
from __future__ import division # ensure things like 1/2 is 0.5 rather than 0
from collections import defaultdict
fh = open("dna.fasta","r")
alllines = fh.readlines()
fh2 = open("dna_stats.txt","w")
seq=0
data = dict()
for line in alllines:
if line.startswith(">"):
seq+=1
data[seq]=defaultdict(int) #default value will be zero if key is not present hence we can do +=1 without originally initializing to zero
data[seq]['seq']=seq
previous_line_end = "" #TGA might be split accross line
continue
data[seq]['Acount']+=line.count("A")
data[seq]['Ccount']+=line.count("C")
data[seq]['Gcount']+=line.count("G")
data[seq]['Tcount']+=line.count("T")
data[seq]['genomeSize']+=data[seq]['Acount']+data[seq]['Gcount']+data[seq]['Ccount']+data[seq]['Tcount']
line_over = previous_line_end + line[:3]
data[seq]['hasTGA']= data[seq]['hasTGA'] or ("TGA" in line) or (TGA in line_over)
previous_line_end = str.strip(line[-4:]) #save previous_line_end for next line removing new line character.
for seq in data.keys():
data[seq]['percentGC']=(data[seq]['Gcount']+data[seq]['Ccount'])*100.00/data[seq]['genomeSize']
s = '%(seq)d, %(genomeSize)d, %(Acount)d, %(Ccount)d, %(Tcount)d, %(Tcount)d, %(percentGC).2f, %(hasTGA)s'
fh2.write(s % data[seq])
fh.close()
fh2.close()

matching and dispalying specific lines through python

I have 15 lines in a log file and i want to read the 4th and 10 th line for example through python and display them on output saying this string is found :
abc
def
aaa
aaa
aasd
dsfsfs
dssfsd
sdfsds
sfdsf
ssddfs
sdsf
f
dsf
s
d
please suggest through code how to achieve this in python .
just to elaborate more on this example the first (string or line is unique) and can be found easily in logfile the next String B comes within 40 lines of the first one but this one occurs at lots of places in the log file so i need to read this string withing the first 40 lines after reading string A and print the same that these strings were found.
Also I cant use with command of python as this gives me errors like 'with' will become a reserved keyword in Python 2.6. I am using Python 2.5

You can use this:
fp = open("file")
for i, line in enumerate(fp):
if i == 3:
print line
elif i == 9:
print line
break
fp.close()

def bar(start,end,search_term):
with open("foo.txt") as fil:
if search_term in fil.readlines()[start,end]:
print search_term + " has found"
>>>bar(4, 10, "dsfsfs")
"dsfsfs has found"

#list of random characters
from random import randint
a = list(chr(randint(0,100)) for x in xrange(100))
#look for this
lookfor = 'b'
for element in xrange(100):
if lookfor==a[element]:
print a[element],'on',element
#b on 33
#b on 34
is one easy to read and simple way to do it. Can you give part of your log file as an example? There are other ways that may work better :).
after edits by author:
The easiest thing you can do then is:
looking_for = 'findthis' i = 1 for line in open('filename.txt','r'):
if looking_for == line:
print i, line
i+=1
it's efficient and easy :)

How to process the output from a command invoked by python

I want to write a python program, that invokes ipcs and uses its output to delete shared memory segments and semaphores.
I have a working solution, but feel there must be a better way to do this.
Here is my program:
import subprocess
def getid(ip):
ret=''
while (output[ip]==' '):
ip=ip+1
while((output[ip]).isdigit()):
ret=ret+output[ip]
ip=ip+1
return ret
print 'invoking ipcs'
output = subprocess.check_output(['ipcs'])
print output
for i in range (len(output)):
if (output[i]=='m'):
r=getid(i+1)
print r
if (r):
op = subprocess.check_output(['ipcrm','-m',r])
print op
elif (output[i]=='s'):
r=getid(i+1)
print r
if (r):
op = subprocess.check_output(['ipcrm','-s',r])
print op
print 'invoking ipcs'
output = subprocess.check_output(['ipcs'])
print output
In particular, is there a better way to write "getid"? ie instead of parsing it character by character,
can I parse it string by string?
This is what the output variable looks like (before parsing):
Message Queues:
T ID KEY MODE OWNER GROUP
Shared Memory:
T ID KEY MODE OWNER GROUP
m 262144 0 --rw-rw-rw- xyz None
m 262145 0 --rw-rw-rw- xyz None
m 262146 0 --rw-rw-rw- xyz None
m 196611 0 --rw-rw-rw- xyz None
m 196612 0 --rw-rw-rw- xyz None
m 262151 0 --rw-rw-rw- xyz None
Semaphores:
T ID KEY MODE OWNER GROUP
s 262144 0 --rw-rw-rw- xyz None
s 262145 0 --rw-rw-rw- xyz None
s 196610 0 --rw-rw-rw- xyz None
Thanks!

You can pipe in the output from ipcs line by line as it outputs it. Then I would use .strip().split() to parse each line, and something like a try except block to make sure the line fits your criteria. Parsing it as a stream of characters makes things more complicated, I wouldn't recommend it..
import subprocess
proc = subprocess.Popen(['ipcs'],stdout=subprocess.PIPE)
for line in iter(proc.stdout.readline,''):
line=line.strip().split()
try:
r = int(line[1])
except:
continue
if line[0] == "m":
op = subprocess.check_output(['ipcrm','-m',str(r)])
elif line[0] == "s":
op = subprocess.check_output(['ipcrm','-s',str(r)])
print op
proc.wait()

There is really no need to iterate over the output one char at a time.
For one, you should split the output string in lines and iterate over those, handling one at a time. That is done by using the splitlines method of strings (see the docs for details).
You could further split the lines on blanks, using split(), but given the regularity of your output, a regular expression fits the bill nicely. Basically, if the first character is either m or s, the next number of digits is your id, and whether m or s matches decides your next action.
You can use names to identify the groups of characters you identified, which makes for an easier reading of the regular expression and more comfortable handling of the result due to groupdict.
import re
pattern = re.compile('^((?P<mem>m)|(?P<sem>s))\s+(?P<id>\d+)')
for line in output.splitlines():
m = pattern.match(line)
if m:
groups = m.groupdict()
_id = groups['id']
if groups['mem']:
print 'handling a memory line'
pass # handle memory case
else:
print ' handling a semaphore line'
pass # handle semaphore case

You could use the string split method to split the string based on the spaces in it.
So you could use,
for line in output:
if (line.split(" ")[0] == 'm')):
id = line.split(" ")[2]
print id

Python split string on quotes

I'm a python learner. If I have a lines of text in a file that looks like this
"Y:\DATA\00001\SERVER\DATA.TXT" "V:\DATA2\00002\SERVER2\DATA2.TXT"
Can I split the lines around the inverted commas? The only constant would be their position in the file relative to the data lines themselves. The data lines could range from 10 to 100+ characters (they'll be nested network folders). I cannot see how I can use any other way to do those markers to split on, but my lack of python knowledge is making this difficult.
I've tried
optfile=line.split("")
and other variations but keep getting valueerror: empty seperator. I can see why it's saying that, I just don't know how to change it. Any help is, as always very appreciated.
Many thanks

You must escape the ":
input.split("\"")
results in
['\n',
'Y:\\DATA\x0001\\SERVER\\DATA.TXT',
' ',
'V:\\DATA2\x0002\\SERVER2\\DATA2.TXT',
'\n']
To drop the resulting empty lines:
[line for line in [line.strip() for line in input.split("\"")] if line]
results in
['Y:\\DATA\x0001\\SERVER\\DATA.TXT', 'V:\\DATA2\x0002\\SERVER2\\DATA2.TXT']

I'll just add that if you were dealing with lines that look like they could be command line parameters, then you could possibly take advantage of the shlex module:
import shlex
with open('somefile') as fin:
for line in fin:
print shlex.split(line)
Would give:
['Y:\\DATA\\00001\\SERVER\\DATA.TXT', 'V:\\DATA2\\00002\\SERVER2\\DATA2.TXT']

No regex, no split, just use csv.reader
import csv
sample_line = '10.0.0.1 foo "24/Sep/2015:01:08:16 +0800" www.google.com "GET /" -'
def main():
for l in csv.reader([sample_line], delimiter=' ', quotechar='"'):
print l
The output is
['10.0.0.1', 'foo', '24/Sep/2015:01:08:16 +0800', 'www.google.com', 'GET /', '-']

shlex module can help you.
import shlex
my_string = '"Y:\DATA\00001\SERVER\DATA.TXT" "V:\DATA2\00002\SERVER2\DATA2.TXT"'
shlex.split(my_string)
This will spit
['Y:\\DATA\x0001\\SERVER\\DATA.TXT', 'V:\\DATA2\x0002\\SERVER2\\DATA2.TXT']
Reference: https://docs.python.org/2/library/shlex.html

Finding all regular expression matches will do it:
input=r'"Y:\DATA\00001\SERVER\DATA.TXT" "V:\DATA2\00002\SERVER2\DATA2.TXT"'
re.findall('".+?"', # or '"[^"]+"', input)
This will return the list of file names:
["Y:\DATA\00001\SERVER\DATA.TXT", "V:\DATA2\00002\SERVER2\DATA2.TXT"]
To get the file name without quotes use:
[f[1:-1] for f in re.findall('".+?"', input)]
or use re.finditer:
[f.group(1) for f in re.finditer('"(.+?)"', input)]

The following code splits the line at each occurrence of the inverted comma character (") and removes empty strings and those consisting only of whitespace.
[s for s in line.split('"') if s.strip() != '']
There is no need to use regular expressions, an escape character, some module or assume a certain number of whitespace characters between the paths.
Test:
line = r'"Y:\DATA\00001\SERVER\DATA.TXT" "V:\DATA2\00002\SERVER2\DATA2.TXT"'
output = [s for s in line.split('"') if s.strip() != '']
print(output)
>>> ['Y:\\DATA\\00001\\SERVER\\DATA.TXT', 'V:\\DATA2\\00002\\SERVER2\\DATA2.TXT']

I think what you want is to extract the filepaths, which are separated by spaces. That is you want to split the line about items contained within quotations. I.e with a line
"FILE PATH" "FILE PATH 2"
You want
["FILE PATH","FILE PATH 2"]
In which case:
import re
with open('file.txt') as f:
for line in f:
print(re.split(r'(?<=")\s(?=")',line))
With file.txt:
"Y:\DATA\00001\SERVER\DATA MINER.TXT" "V:\DATA2\00002\SERVER2\DATA2.TXT"
Outputs:
>>>
['"Y:\\DATA\\00001\\SERVER\\DATA MINER.TXT"', '"V:\\DATA2\\00002\\SERVER2\\DATA2.TXT"']

This was my solution. It parses most sane input exactly the same as if it was passed into the command line directly.
import re
def simpleParse(input_):
def reduce_(quotes):
return '' if quotes.group(0) == '"' else '"'
rex = r'("[^"]*"(?:\s|$)|[^\s]+)'
return [re.sub(r'"{1,2}',reduce_,z.strip()) for z in re.findall(rex,input_)]
Use case: Collecting a bunch of single shot scripts into a utility launcher without having to redo command input much.
Edit:
Got OCD about the stupid way that the command line handles crappy quoting and wrote the below:
import re
tokens = list()
reading = False
qc = 0
lq = 0
begin = 0
for z in range(len(trial)):
char = trial[z]
if re.match(r'[^\s]', char):
if not reading:
reading = True
begin = z
if re.match(r'"', char):
begin = z
qc = 1
else:
begin = z - 1
qc = 0
lc = begin
else:
if re.match(r'"', char):
qc = qc + 1
lq = z
elif reading and qc % 2 == 0:
reading = False
if lq == z - 1:
tokens.append(trial[begin + 1: z - 1])
else:
tokens.append(trial[begin + 1: z])
if reading:
tokens.append(trial[begin + 1: len(trial) ])
tokens = [re.sub(r'"{1,2}',lambda y:'' if y.group(0) == '"' else '"', z) for z in tokens]

I know this got answered a million year ago, but this works too:
input = '"Y:\DATA\00001\SERVER\DATA.TXT" "V:\DATA2\00002\SERVER2\DATA2.TXT"'
input = input.replace('" "','"').split('"')[1:-1]
Should output it as a list containing:
['Y:\\DATA\x0001\\SERVER\\DATA.TXT', 'V:\\DATA2\x0002\\SERVER2\\DATA2.TXT']

My question Python - Error Caused by Space in argv Arument was marked as a duplicate of this one. We have a number of Python books doing back to Python 2.3. The oldest referred to using a list for argv, but with no example, so I changed things to:-
repoCmd = ['Purchaser.py', 'task', repoTask, LastDataPath]
SWCore.main(repoCmd)
and in SWCore to:-
sys.argv = args
The shlex module worked but I prefer this.