Re: More Help with python .find fucntion
THanks ... I am new to Python ... Comparing the result of find with -1 fixes the bug ... some of the endobj start in the firt position ... You're right about the lines ending in \n by accident, EXCEPT in PDF files items are separated by obj \n and endobj\n -- - --- -- - Posted with NewsLeecher v4.0 Final Web @ http://www.newsleecher.com/?usenet --- - -- - -- http://mail.python.org/mailman/listinfo/python-list
More Help with python .find fucntion
My previous question asked how to read a file into a strcuture
a line at a time. Figured it out. Now I'm trying to use .find
to separate out the PDF objects. (See code) PROBLEM/QUESTION:
My call to lines[i].find does NOT find all instances of endobj.
Any help available? Any insights?
#!/usr/bin/python
inputfile = file('sample.pdf','rb')# This is PDF with which we
will work
lines = inputfile.readlines() # read file one line at a time
linestart = [] # Starting address for each line
lineend = []# Ending address for each line
linetype = []
print len(lines)# print number of lines
i = 0 # define an iterator, i
addr = 0# and address pointer
while i len(lines): # Go through each line
linestart = linestart + [addr]
length = len(lines[i])
lineend = lineend + [addr + (length-1)]
addr = addr + length
i = i + 1
i = 0
while i len(lines): # Initialize line types as
normal
linetype = linetype + ['normal']
i = i + 1
i = 0
while i len(lines): #
if lines[i].find(' obj') 0:
linetype[i] = 'object'
print At address ,linestart[i],object found at line ,i,: ,
lines[i]
if lines[i].find('endobj') 0:
linetype[i] = 'endobj'
print At address ,linestart[i],endobj found at line ,i,: ,
lines[i]
i = i + 1
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Re: More Help with python .find fucntion
On Fri, Jan 7, 2011 at 8:43 PM, Keith Anthony kanth...@woh.rr.com wrote:
My previous question asked how to read a file into a strcuture
a line at a time. Figured it out. Now I'm trying to use .find
to separate out the PDF objects. (See code) PROBLEM/QUESTION:
My call to lines[i].find does NOT find all instances of endobj.
Any help available? Any insights?
#!/usr/bin/python
inputfile = file('sample.pdf','rb') # This is PDF with which we
will work
lines = inputfile.readlines() # read file one line at a time
linestart = [] # Starting address for each
line
lineend = [] # Ending address for each line
linetype = []
print len(lines) # print number of lines
i = 0 # define an iterator, i
addr = 0 # and address pointer
while i len(lines): # Go through each line
linestart = linestart + [addr]
length = len(lines[i])
lineend = lineend + [addr + (length-1)]
addr = addr + length
i = i + 1
i = 0
while i len(lines): # Initialize line types as
normal
linetype = linetype + ['normal']
i = i + 1
i = 0
while i len(lines): #
if lines[i].find(' obj') 0:
linetype[i] = 'object'
print At address ,linestart[i],object found at line ,i,: ,
lines[i]
if lines[i].find('endobj') 0:
linetype[i] = 'endobj'
print At address ,linestart[i],endobj found at line ,i,: ,
lines[i]
i = i + 1
Your code can be simplified significantly.
In particular:
- Don't add single-element lists. Use the list.append() method instead.
- One seldom manually tracks counters like `i` in Python; use range()
or enumerate() instead.
- Lists have a multiply method which gives the concatenation of n
copies of the list.
Revised version (untested obviously):
inputfile = file('sample.pdf','rb')# This is PDF with
which we will work
lines = inputfile.readlines() # read file one line at a time
linestart = [] # Starting address for each line
lineend = []# Ending address for each line
linetype = ['normal']*len(lines)
print len(lines)# print number of lines
addr = 0# and address pointer
for line in lines: # Go through each line
linestart.append(addr)
length = len(line)
lineend.append(addr + (length-1))
addr += length
for i, line in enumerate(lines):
if line.find(' obj') 0:
linetype[i] = 'object'
print At address ,linestart[i],object found at line ,i,: , line
if line.find('endobj') 0:
linetype[i] = 'endobj'
print At address ,linestart[i],endobj found at line ,i,: , line
As to the bug: I think you want != -1 rather than 0 for your
conditionals; remember that Python list/string indices are 0-based.
Cheers,
Chris
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Re: More Help with python .find fucntion
On Fri, 07 Jan 2011 22:43:54 -0600, Keith Anthony wrote:
My previous question asked how to read a file into a strcuture a line at
a time. Figured it out. Now I'm trying to use .find to separate out
the PDF objects. (See code) PROBLEM/QUESTION: My call to lines[i].find
does NOT find all instances of endobj. Any help available? Any
insights?
#!/usr/bin/python
inputfile = file('sample.pdf','rb')# This is PDF with which
we will work
lines = inputfile.readlines() # read file
one line at a time
That's incorrect. readlines() reads the entire file in one go, and splits
it into individual lines.
linestart = [] # Starting address for
each line
lineend = []# Ending
address for each line
linetype = []
*raises eyebrow*
How is an empty list a starting or ending address?
The only thing worse than no comments where you need them is misleading
comments. A variable called linestart implies that it should be a
position, e.g. linestart = 0. Or possibly a flag.
print len(lines)# print number of lines
i = 0 # define an iterator, i
Again, 0 is not an iterator. 0 is a number.
addr = 0# and address pointer
while i len(lines): # Go through each line
linestart = linestart + [addr]
length = len(lines[i])
lineend = lineend + [addr + (length-1)] addr = addr + length
i = i + 1
Complicated and confusing and not the way to do it in Python. Something
like this is much simpler:
linetypes = [] # note plural
inputfile = open('sample.pdf','rb') # Don't use file, use open.
for line_number, line in enumerate(inputfile):
# Process one line at a time. No need for that nonsense with manually
# tracked line numbers, enumerate() does that for us.
# No need to initialise linetypes.
status = 'normal'
i = line.find(' obj')
if i = 0:
print Object found at offset %d in line %d % (i, line_number)
status = 'object'
i = line.find('endobj')
if i = 0:
print endobj found at offset %d in line %d % (i, line_number)
if status == 'normal': status = 'endobj'
else: status = 'object endobj' # both found on the one line
linetypes.append(status)
# What if obj or endobj exist more than once in a line?
One last thing... if PDF files are a binary format, what makes you think
that they can be processed line-by-line? They may not have lines, except
by accident.
--
Steven
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