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)
Related
I'm trying to run this script using the code
subprocess.call(["php C:\Python27\a.php"])
and I'm getting this error:
FileNotFoundError: [WinError 2] The system cannot find the file specified
i have tried changing path but nothing seems to work, any ideas?
Either
subprocess.call(["php", "C:\\Python27\\a.php"])
or
subprocess.call(["php", r"C:\Python27\a.php"])
should work.
Try this:
subprocess.call(["php", "C:\\Python27\\a.php"])
From the documentation:
args is required for all calls and should be a string, or a sequence
of program arguments. Providing a sequence of arguments is generally
preferred, as it allows the module to take care of any required
escaping and quoting of arguments (e.g. to permit spaces in file
names). If passing a single string, either shell must be True (see
below) or else the string must simply name the program to be executed
without specifying any arguments.
Also note that in python, like many other languages, the backslash in a normal string has special meaning. You'll have to use double backslashes or a raw string to get the behavior you want.
I need to pass a string value between two python scripts.
It's not an argument but it's a string containing a sentence (with spaces, commas and so on).
example:
one.py has a string variable "hello world, how are you today?"
and I need to pass it to two.py
How can I achieve this result?
It's not an argument but it's a string containing a sentence (with spaces, commas and so on).
Why isn't that an argument?
I don't know how you were planning to run the other script, but pretty much any way of doing so allows you to pass strings with spaces, commas and so on as arguments.
If you're doing things the smart way, it works automatically:
subprocess.check_call([sys.executable, path_to_script2, arg])
If you're doing something like os.system you'll have to quote the argument manually to pass it through the shell… but the easiest answer there is "don't use os.system, so I won't show how to do that unless you ask for it specifically.
Either way, when script2 runs, its sys.argv[1] will be arg, with the spaces and commas and so on preserved.
If the string is too big, you may run into problems with maximum argv length—and, worse, they may be different problems on different platforms.
Also, if you're using Unicode, especially in Python 2.x, there can be some complexities to deal with.
But, for short-ish all-ASCII strings like "hello world, how are you today?", it's all trivial.
I'd suggest using a text document that one script writes to and the other reads from. It's should be pretty simple to implement.
Documentation for reading and writing files can be found here:
http://docs.python.org/2/tutorial/inputoutput.html#reading-and-writing-files
I have the following python script snidbit:
inLines = sys.argv[0]
arcpy.AddMessage(inLines)
The input parameter is a multivalue input whereby the user can navigate to a file locations and choose multiple files as the input.
When I print out the variable, I get the follwoing:
Y:\2012_data\INFRASTRUCTURE.gdb\Buildings;'Z:\DATA FOR
2009\Base.gdb\CREEKS_UTM';'Z:\DATA FOR 2009\Base.gdb\LAKES_UTM'
Notice on the Z:drive, it is returning the path with single quotes around it, whereas the Y:drive does not. I believe this is caused by the spaces in the Z:drive paths. Is there a way to force the Z:drive paths to return without the quotes?
Thanks,
Mike
I managed to solve this issue. Python handles the parameters differently because of the path names. In the first parameter, there are no spaces in the file path. In the other 2 parameters, there are spaces. Python doesn't like spaces, so it forces the file path into a string value. I just wrote some code to override this.
I am calling a python script through a bash wrapper, but I'm having trouble dealing with arguments that contain quoted spaces.
I assemble the arguments to the python script into a bash variable, such as
opt="-c start.txt"
opt+="--self 'name Na'"
Then call the python script with something like:
python test_args.py $opt
When printing sys.argv in Python, I get
['test-args.py', '-c', 'start.txt', '--self', "'name", "Na'"]
instead of the expected
['test-args.py', '-c', 'start.txt', '--self', 'name Na']
I tried using an array when calling the script, such as
python test_args.py ${opt[#]}
but then I get
['test-args.py', "-c start.txt --self 'name Na'"]
Any other ideas?
Use an array, but store each argument as a separate element in the array:
opt=(-c start.txt)
opt+=(--self 'name Na')
python test_args.py "${opt[#]}"
See BashFAQ #050.
This is what the shlex module is for.
The shlex class makes it easy to write lexical analyzers for simple
syntaxes resembling that of the Unix shell. This will often be useful
for writing minilanguages, (for example, in run control files for
Python applications) or for parsing quoted strings.
Your instinct to embed spaces inside the variable's value was good, but when the value is simply expanded during the command line parsing their special meaning is lost as you saw. You need to expand the variable before the command line to your python script is parsed:
set -f
eval python test_args.py $opt
set +f
That will expand to:
python test_args.py -c start.txt --self 'name Na'
Which will then be parsed correctly with the quotes regaining their special meaning.
Edit: I've added set -f/+f (aka -/+o noglob) around the eval to disable file globbing although that wasn't an issue in the OP's example that's not an unheard of issue with eval. (Another, stronger caveat is to never eval user input unless you take extreme care to make sure it won't blow up into something nasty. If you don't control the value being eval-ed, you can't be sure what will happen.)
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')))