I wrote my module in Python 3.1.2, but now I have to validate it for 2.6.4.
I'm not going to post all my code since it may cause confusion.
Brief explanation:
I'm writing a XML parser (my first interaction with XML) that creates objects from the XML file. There are a lot of objects, so I have a 'unit test' that manually scans the XML and tries to find a matching object. It will print out anything that doesn't have a match.
I open the XML file and use a simple 'for' loop to read line-by-line through the file. If I match a regular expression for an 'application' (XML has different 'application' nodes), then I add it to my dictionary, d, as the key. I perform a lxml.etree.xpath() query on the title and store it as the value.
After I go through the whole thing, I iterate through my dictionary, d, and try to match the key to my value (I have to use the get() method from my 'application' class). Any time a mismatch is found, I print the key and title.
Python 3.1.2 has all matching items in the dictionary, so nothing is printed. In 2.6.4, every single value is printed (~600) in all. I can't figure out why my string comparisons aren't working.
Without further ado, here's the relevant code:
for i in d:
if i[1:-2] != d[i].get('id'):
print('X%sX Y%sY' % (i[1:-3], d[i].get('id')))
I slice the strings because the strings are different. Where the key would be "9626-2008olympics_Prod-SH"\n the value would be 9626-2008olympics_Prod-SH, so I have to cut the quotes and newline. I also added the Xs and Ys to the print statements to make sure that there wasn't any kind of whitespace issues.
Here is an example line of output:
X9626-2008olympics_Prod-SHX Y9626-2008olympics_Prod-SHY
Remember to ignore the Xs and Ys. Those strings are identical. I don't understand why Python2 can't match them.
Edit:
So the problem seems to be the way that I am slicing.
In Python3,
if i[1:-2] != d[i].get('id'):
this comparison works fine.
In Python2,
if i[1:-3] != d[i].get('id'):
I have to change the offset by one.
Why would strings need different offsets? The only possible thing that I can think of is that Python2 treats a newline as two characters (i.e. '\' + 'n').
Edit 2:
Updated with requested repr() information.
I added a small amount of code to produce the repr() info from the "2008olympics" exmpale above. I have not done any slicing. It actually looks like it might not be a unicode issue. There is now a "\r" character.
Python2:
'"9626-2008olympics_Prod-SH"\r\n'
'9626-2008olympics_Prod-SH'
Python3:
'"9626-2008olympics_Prod-SH"\n'
'9626-2008olympics_Prod-SH'
Looks like this file was created/modified on Windows. Is there a way in Python2 to automatically suppress '\r'?
You are printing i[1:-3] but comparing i[1:-2] in the loop.
Very Important Question
Why are you writing code to parse XML when lxml will do all that for you? The point of unit tests is to test your code, not to ensure that the libraries you are using work!
Russell Borogrove is right.
Python 3 defaults to unicode, and the newline character is correctly interpreted as one character. That's why my offset of [1:-2] worked in 3 because I needed to eliminate three characters: ", ", and \n.
In Python 2, the newline is being interpreted as two characters, meaning I have to eliminate four characters and use [1:-3].
I just added a manual check for the Python major version.
Here is the fixed code:
for i in d:
# The keys in D contain quotes and a newline which need
# to be removed. In v3, newline = 1 char and in v2,
# newline = 2 char.
if sys.version_info[0] < 3:
if i[1:-3] != d[i].get('id'):
print('%s %s' % (i[1:-3], d[i].get('id')))
else:
if i[1:-2] != d[i].get('id'):
print('%s %s' % (i[1:-2], d[i].get('id')))
Thanks for the responses everyone! I appreciate your help.
repr() and %r format are your friends ... they show you (for basic types like str/unicode/bytes) exactly what you've got, including type.
Instead of
print('X%sX Y%sY' % (i[1:-3], d[i].get('id')))
do
print('%r %r' % (i, d[i].get('id')))
Note leaving off the [1:-3] so that you can see what is in i before you slice it.
Update after comment "You are perfectly right about comparing the wrong slice. However, once I change it, python2.6 works, but python3 has the problem now (i.e. it doesn't match any objects)":
How are you opening the file (two answers please, for Python 2 and 3). Are you running on Windows? Have you tried getting the repr() as I suggested?
Update after actual input finally provided by OP:
If, as it appears, your input file was created on Windows (lines are separated by "\r\n"), you can read Windows and *x text files portably by using the "universal newlines" option ... open('datafile.txt', 'rU') on Python2 -- read this. Universal newlines mode is the default in Python3. Note that the Python3 docs say that you can use 'rU' also in Python3; this would save you having to test which Python version you are using.
I don't understand what you're doing exactly, but would you try using strip() instead of slicing and see whether it helps?
for i in d:
stripped = i.strip()
if stripped != d[i].get('id'):
print('X%sX Y%sY' % (stripped, d[i].get('id')))
Related
I would like to know what this small portion of code means, because it seems like in the file that the script creates it adds a line in the end and i believe it might be one of those symbols
opened_file.write("%s\n" %user_input)
It writes a line. The content of user_input replaces the %s (see string interpolation in the docs) and \n is the newline character - after user_input.
Here is a good description of the different "inserting data into strings" methods, including % interpolation (which is now considered outdated):
https://realpython.com/python-string-formatting/
I need to transform a string containing single and double quotes and newline characters for use in a system call. Consider the following input string:
"""one'two\nthree"four"""
This should be transformed to the following output string:
"$'one\'two\nthree\"four'"
So that it can be submitted as a message argument in a git commit command:
git commit --message=$'one\'two\nthree\"four'
The odd syntax with the leading $ and surrounding single quotes ' is a bash construct described in the bash manpage in the section on quoting (search for QUOTING). I have tried many python functions including str.replace, re.sub, json.dumps, repr, and str.encode('unicode-escape'). But none have yielded the required transformation. It seems that, in this case, python is too high-level for its own good. Suggestions on how to proceed will be very gratefully received.
The system call itself will be made using code like this (omitting the try block for clarity):
import subprocess
call = ["git", "commit", "--message", "'one\'two\nthree\"four'"]
cpi = subprocess.run(call)
I may also use a git library of some description, but I have not done my homework yet for that.
Note: the unnecessary $ character in the last item in the above call list has been removed.
Your wanted command is erroneous at the moment, it is not a valid Python string since a right " is missing, it should be:
"$'one\'two\nthree\"four'"
This is easily constructed by a simple .format call:
>>> "$'{}'".format("""one'two\nthree"four""") == "$'one\'two\nthree\"four'"
True
So I'm trying to parse a bunch of citations from a text file using the re module in python 3.4 (on, if it matters, a mac running mavericks). Here's some minimal code. Note that there are two commented lines: they represent two alternative searches. (Obviously, the little one, r'Rawls', is the one that works)
def makeRefList(reffile):
print(reffile)
# namepattern = r'(^[A-Z1][A-Za-z1]*-?[A-Za-z1]*),.*( \(?\d\d\d\d[a-z]?[.)])'
# namepattern = r'Rawls'
refsTuplesList = re.findall(namepattern, reffile, re.MULTILINE)
print(refsTuplesList)
The string in question is ugly, and so I stuck it in a gist: https://gist.github.com/paultopia/6c48c398a42d4834f2ae
As noted, the search string r'Rawls' produces expected output ['Rawls', 'Rawls']. However, the other search string just produces an empty list.
I've confirmed this regex (partially) works using the regex101 tester. Confirmation here: https://regex101.com/r/kP4nO0/1 -- this match what I expect it to match. Since it works in the tester, it should work in the code, right?
(n.b. I copied the text from terminal output from the first print command, then manually replaced \n characters in the string with carriage returns for regex101.)
One possible issue is that python has appended the bytecode flag (is the little b called a "flag?") to the string. This is an artifact of my attempt to convert the text from utf-8 to ascii, and I haven't figured out how to make it go away.
Yet re clearly is able to parse strings in that form. I know this because I'm converting two text files from utf-8 to ascii, and the following code works perfectly fine on the other string, converted from the other text file, which also has a little b in front of it:
def makeCiteList(citefile):
print(citefile)
citepattern = r'[\s(][A-Z1][A-Za-z1]*-?[A-Za-z1]*[ ,]? \(?\d\d\d\d[a-z]?[\s.,)]'
rawCitelist = re.findall(citepattern, citefile)
cleanCitelist = cleanup(rawCitelist)
finalCiteList = list(set(cleanCitelist))
print(finalCiteList)
return(finalCiteList)
The other chunk of text, which the code immediately above matches correctly: https://gist.github.com/paultopia/a12eba2752638389b2ee
The only hypothesis I can come up with is that the first, broken, regex expression is puking on the combination of newline characters and the string being treated as a byte object, even though a) I know the regex is correct for newlines (because, confirmation from the linked regex101), and b) I know it's matching the strings (because, confirmation from the successful match on the other string).
If that's true, though, I don't know what to do about it.
Thus, questions:
1) Is my hypothesis right that it's the combination of newlines and b that blows up my regex? If not, what is?
2) How do I fix that?
a) replace the newlines with something in the string?
b) rewrite the regex somehow?
c) somehow get rid of that b and make it into a normal string again? (how?)
thanks!
Addition
In case this is a problem I need to fix upstream, here's the code I'm using to get the text files and convert to ascii, replacing non-ascii characters:
this function gets called on utf-8 .txt files saved by textwrangler in mavericks
def makeCorpoi(citefile, reffile):
citebox = open(citefile, 'r')
refbox = open(reffile, 'r')
citecorpus = citebox.read()
refcorpus = refbox.read()
citebox.close()
refbox.close()
corpoi = [str(citecorpus), str(refcorpus)]
return corpoi
and then this function gets called on each element of the list the above function returns.
def conv2ASCII(bigstring):
def convHandler(error):
return ('1FOREIGN', error.start + 1)
codecs.register_error('foreign', convHandler)
bigstring = bigstring.encode('ascii', 'foreign')
stringstring = str(bigstring)
return stringstring
Aah. I've tracked it down and answered my own question. Apparently one needs to call some kind of encode method on the decoded thing. The following code produces an actual string, with newlines and everything, out the other end (though now I have to fix a bunch of other bugs before I can figure out if the final output is as expected):
def conv2ASCII(bigstring):
def convHandler(error):
return ('1FOREIGN', error.start + 1)
codecs.register_error('foreign', convHandler)
bigstring = bigstring.encode('ascii', 'foreign')
newstring = bigstring.decode('ascii', 'foreign')
return newstring
apparently the str() function doesn't do the same job, for reasons that are mysterious to me. This is despite an answer here How to make new line commands work in a .txt file opened from the internet? which suggests that it does.
I am quite new to python and i struck an issue wherein, I am dynamically retrieving a string from a dictionary which looks like this
files="eputilities/epbalancing_alb/referenced assemblies/model/cv6_xmltypemodel_xp2.cs"
I am unable to to perform any actions on this particular file as it is reading the path as 2 different strings
eputilities/epbalancing_alb/referenced and assemblies/model/cv6_xmltypemodel_xp2.cs
as there is a space between referenced and assemblies.
I wanted to know how to convert this to raw_string (ignore the space, but still keep the space between the two and consider it as one string)
I'm not able to figure this out although several comments where there on the web.
Please do help.
Thanks
From the comments to the other answer, I understand that you want to execute some external tool and pass a parameter (a filename) to it. This parameter, however, has spaces in it.
I'd propose to approaches; definitely, I'd use subprocess, not os.system.
import subprocess
# Option 1
subprocess.call([path_to_executable, parameter])
# Option 2
subprocess.call("%s \"%s\"" % (path_to_executable, parameter), shell=True)
For me, both worked, please check if they work yor you as well.
Explanations:
Option 1 takes a list of strings, where the first string has to be the path to the executable and all others are interpreted as command line arguments. As subprocess.call knows about each of these entities, it properly calls the external so that it understand thatparameter` is to be interpreted as one string with spaces - and not as two or more parameters.
Option 2 is different. With the keyword-argument shell=True we tell subprocess.call to execute the call through a shell, i.e., the first positional argument is "interpreted as if it was typed like this in a shell". But now, we have to prepare this string accordingly. So what would you do if you had to type a filename with spaces as a parameter? You'd put it between double quotes. This is what I do here.
Standard string building in python works like this
'%s foo %s'%(str_val_1, str_val_2)
So if I'm understanding you right either have a list of two strings or two different string variables.
For the prior do this:
' '.join(list)
For the latter do this:
'%s %s'%(string_1, string_2)
I'm outputting pretty huge XML structure to file and I want user to be able to enable/disable pretty print.
I'm working with approximately 150MB of data,when I tried xml.etree.ElementTree and build tree structure from it's element objects, it used awfully lot of memory, so I do this manually by storing raw strings and outputing by .write(). My output sequence looks like this:
ofile.write(pretty_print(u'\
\t\t<LexicalEntry id="%s">\n\
\t\t\t<feat att="languageCode" val="cz"/>\n\
\t\t\t<Lemma>\n\
\t\t\t\t<FormRepresentation>\n\
\t\t\t\t\t<feat att="writtenForm" val="%s"/>\n\
\t\t\t\t</FormRepresentation>\n\
\t\t\t</Lemma>\n\
\t\t\t<Sense>%s\n' % (str(lex_id), word['word'], '' if word['pos']=='' else '\n\t\t\t\t<feat att="partOfSpeech" val="%s"/>' % word['pos'])))
inside the .write() I call my function pretty_print which, depending on command line option, SHOULD strip all tab and newline characters
o_parser = OptionParser()
# ....
o_parser.add_option("-p", "--prettyprint", action="store_true", dest="pprint", default=False)
# ....
def pretty_print(string):
if not options.pprint:
return string.strip('\n\t')
return string
I wrote 'should', because it does not, in this particular case it does not strip any of the characters.
BUT in this case, it works fine:
for ss in word['synsets']:
ofile.write(pretty_print(u'\t\t\t\t<Sense synset="%s-synset"/>\n' % ss))
First thing that came on my mind was that there might be some issues with the substitution, but when i print passed string inside the pretty_print function it looks perfectly fine.
Any suggestiones what might cause that .strip() does not work?
Or if there is any better way to do this, I'll accept any advice
Your issue is that str.strip() only removes from the beginning and end of a string.
You either want str.replace() to remove all instances, or to split it into lines and strip each line, if you want to remove them from the beginning and end of lines.
Also note that for your massive string, Python supports multi-line strings with triple quotes that will make it a lot easier to type out, and the old style string formatting with % has been superseded by str.format() - which you probably want to use instead in new code.