I'm trying to set up an environment variable via Python:
os.environ["myRoot"]="/home/myName"
os.environ["subDir"]="$myRoot/subDir"
I expect the subDir environment variable to hold /home/myname/subDir, however it holds the string '$myRoot/subDir'. How do I get this functionality?
(Bigger picture : I'm reading a json file of environment variables and the ones lower down reference the ones higher up)
Use os.environ to fetch the value, and os.path to correctly put slashes in the right places:
os.environ["myRoot"]="/home/myName"
os.environ["subDir"] = os.path.join(os.environ['myRoot'], "subDir")
You can use os.path.expandvars to expand environment variables like so:
>>> import os
>>> print os.path.expandvars("My home directory is $HOME")
My home director is /home/Majaha
>>>
For your example, you might do:
os.environ["myRoot"] = "/home/myName"
os.environ["subDir"] = os.path.expandvars("$myRoot/subDir")
I think #johntellsall's answer is the better for the specific example you gave, however I don't doubt you'll find this useful for your json work.
Edit: I would now recommend using #johntellsall's answer, as os.path.expandvars() is designed explicitly for use with paths, so using it for arbitrary strings may work but is kinda hacky.
def fix_text(txt,data):
'''txt is the string to fix, data is the dictionary with the variable names/values'''
def fixer(m): #takes a regex match
match = m.groups()[0] #since theres only one thats all we worry about
#return a replacement or the variable name if its not in the dictionary
return data.get(match,"$%s"%match)
return re.sub("$([a-zA-Z]+)",fixer,txt) #regular expression to match a "$" followed by 1 or more letters
with open("some.json") as f: #open the json file to read
file_text= f.read()
data = json.loads(file_text) #load it into a json object
#try to ensure you evaluate them in the order you found them
keys = sorted(data.keys() ,key=file_text.index)
#create a new dictionary by mapping our ordered keys above to "fixed" strings that support simple variables
data2= dict(map(lambda k:(k,fixer(data[k],data)),keys)
#sanity check
print data2
[edited to fix a typo that would cause it not to work]
Related
I'm trying to use the "ls" python command in maya, to list certain objects with a matching string in the name in concatination with a wildcard.
Simple sample code like this:
from maya.cmds import *
list = ls('mesh*')
This code works and will return a list of objects with the matching string in the name, however, I would like to use a variable instead of hard coding in the string. More like this:
from maya.cmds import *
name = 'mesh'
list = ls('name*')
OR like this:
from maya.cmds import *
name = 'mesh'
list = ls('name' + '*')
However, in both examples, it returns an empty list unlike the first. I'm not sure why this is the case because in those examples, the string concatination should come out to 'mesh*' like the first example. I couldn't find an answer on this website, so I chose to ask a question.
Thank you.
JD
PS. If there is a better way to query for objects in maya, let me know what it's called and I'll do some research into what that is. At the moment, this is the only way I know of how to search for objects in maya.
As soon as you add quotes around your variable name like this 'name', you are actually just creating a new string instead of referring to the variable.
There are many different ways to concatenate a string in Python to achieve what you want:
Using %:
'name%s' % '*'
Using the string's format method:
'{}*'.format(name)
Simply using +:
name + '*'
All of these will yield the same output, 'mesh*', and will work with cmds.ls
Personally I stick with format, and this page demonstrates a lot of reasons why.
I am using Config Parser to specify a list of variables, and the values for those variables are then pulled from a larger file. The variables/lines in the larger file all look like this:
callCount.1.cell=2
callCount.2.cell=10
callCount.3.cell=12
Rather than listing all these variables specifically, would I be able to use an '*' as a wildcard character, in place of the number, like this:
[variablesToPull]
callCount.*.cell
I can't change the formatting of the larger file I'm pulling values from, and I don't always know what the numbers that are apart of the variables will be.
EDIT: I'm using Python 2.7 to do all my Config Parsing
After looking around for a while I don't think it's possible. I ended up using just the first part of the desired variable name in the config file
[variablesToPull]
callCount
Then I created a dictionary from the file I was storing the full list of variable names and values in (All the following code is for Python 2.7, it probably works for Python 3, but might need some syntax changes)
f = open(variable_names_and_values_file, 'r')
dict_of_vars= {}
for line in f:
k, v = line.strip().split('=')
dict_of_vars[k.strip()] = v.strip()
f.close()
Then I looped over this dictionary and created a new list of the specific variables to pull (like callCount.1.cell, callCount.2.cell, ect...)
new_variables= []
for var in partial_variable_names_from_config_file:
for data in dict_of_vars:
if var in data:
new_variables.append(data)
Initially I didn't want to do so much looping for fear of performance decrease (my file of variables has like 10000 lines), but it doesn't seem to have slowed down my script by a noticeable amount.
Hope this helps someone out there
I try to get all values from section in my ini file (via configparser) as a variable:
hue310section = dict(parser.items('HUE_310'))
for keys, value in hue310section.items():
pairs = keys + ' = ' + value
print(pairs)
it gave me partnewfilepath = http://some_site:PORT/about, but I don't know how to import this output as an python variable, that I can use partnewfilepath somewhere in my code. Of course one section will have more values than only one, and I want to change all that in variable. I trying to find solution but I think I miss something because my knowledge about python is not enough yet. I think I need to rebuilt my for statement but don't have a clue how to do it in this particular problem.
My config.ini file looks like:
[HUE_310]
partNewFilePath = ${common:domain}/about
otherValues = something
nextvalue = another something
UPDATE:
I think I need to elaborate more about what I want to achieve. In other part of my code I check version of site I want to process. If the site has, let say version 3.10 I want to get all values from section HUE_310 from my ini file, and use them as python variable. Rest of my code use those variable and if the site version will change I can get values from other section from my ini file and get those values to python variable and use them. I assume that some variables will change from version to version and that's why I want to prepare my code to check this. Also it gives me some freedom to modify some variable if site will change.
I hope it is now more clear.
You don't need a new variable or a for loop, you already have hue310section dict.
You can just use
hue310section['partNewFilePath']
which will be equal to
"http://some_site:PORT/about"
Note that after hue310section = dict(parser.items('HUE_310'))
, otherValues and nextvalue keys will also be defined.
from configobj import ConfigObj
parser_data = ConfigObj(config_path)
current = parser_data['HUE_310'].get('partNewFilePath', 'http://www.default.com')
config_path is path to the file
http://www.default.com is the default value in case that particular key is not found.
I am trying to name keys in my dictionary in a generic way because the name will be based on the data I get from a file. I am a new beginner to Python and I am not able to solve it, hope to get answer from u guys.
For example:
from collections import defaultdict
dic = defaultdict(dict)
dic = {}
if cycle = fergurson:
dic[cycle] = {}
if loop = mourinho:
a = 2
dic[cycle][loop] = {a}
Sorry if there is syntax error or any other mistake.
The variable fergurson and mourinho will be changing due to different files that I will import later on.
So I am expecting to see my output when i type :
dic[fergurson][mourinho]
the result will be:
>>>dic[fergurson][mourinho]
['2']
It will be done by using Python
Naming things, as they say, is one of the two hardest problems in Computer Science. That and cache invalidation and off-by-one errors.
Instead of focusing on what to call it now, think of how you're going to use the variable in your code a few lines down.
If you were to read code that was
for filename in directory_list:
print filename
It would be easy to presume that it is printing out a list of filenames
On the other hand, if the same code had different names
for a in b:
print a
it would be a lot less expressive as to what it is doing other than printing out a list of who knows what.
I know that this doesn't help what to call your 'dic' variable, but I hope that it gets you on the right track to find the right one for you.
i have found a way, if it is wrong please correct it
import re
dictionary={}
dsw = "I am a Geography teacher"
abc = "I am a clever student"
search = re.search(r'(?<=Geography )(.\w+)',dsw)
dictionary[search]={}
again = re.search(r'(?<=clever )(.\w+)' abc)
dictionary[search][again]={}
number = 56
dictionary[search][again]={number}
and so when you want to find your specific dictionary after running the program:
dictionary["teacher"]["student"]
you will get
>>>'56'
This is what i mean to
I'm working through a book called "Head First Programming," and there's a particular part where I'm confused as to why they're doing this.
There doesn't appear to be any reasoning for it, nor any explanation anywhere in the text.
The issue in question is in using multiple-assignment to assign split data from a string into a hash (which doesn't make sense as to why they're using a hash, if you ask me, but that's a separate issue). Here's the example code:
line = "101;Johnny 'wave-boy' Jones;USA;8.32;Fish;21"
s = {}
(s['id'], s['name'], s['country'], s['average'], s['board'], s['age']) = line.split(";")
I understand that this will take the string line and split it up into each named part, but I don't understand why what I think are keys are being named by using a string, when just a few pages prior, they were named like any other variable, without single quotes.
The purpose of the individual parts is to be searched based on an individual element and then printed on screen. For example, being able to search by ID number and then return the entire thing.
The language in question is Python, if that makes any difference. This is rather confusing for me, since I'm trying to learn this stuff on my own.
My personal best guess is that it doesn't make any difference and that it was personal preference on part of the authors, but it bewilders me that they would suddenly change form like that without it having any meaning, and further bothers me that they don't explain it.
EDIT: So I tried printing the id key both with and without single quotes around the name, and it worked perfectly fine, either way. Therefore, I'd have to assume it's a matter of personal preference, but I still would like some info from someone who actually knows what they're doing as to whether it actually makes a difference, in the long run.
EDIT 2: Apparently, it doesn't make any sense as to how my Python interpreter is actually working with what I've given it, so I made a screen capture of it working https://www.youtube.com/watch?v=52GQJEeSwUA
I don't understand why what I think are keys are being named by using a string, when just a few pages prior, they were named like any other variable, without single quotes
The answer is right there. If there's no quote, mydict[s], then s is a variable, and you look up the key in the dict based on what the value of s is.
If it's a string, then you look up literally that key.
So, in your example s[name] won't work as that would try to access the variable name, which is probably not set.
EDIT: So I tried printing the id key both with and without single
quotes around the name, and it worked perfectly fine, either way.
That's just pure luck... There's a built-in function called id:
>>> id
<built-in function id>
Try another name, and you'll see that it won't work.
Actually, as it turns out, for dictionaries (Python's term for hashes) there is a semantic difference between having the quotes there and not.
For example:
s = {}
s['test'] = 1
s['othertest'] = 2
defines a dictionary called s with two keys, 'test' and 'othertest.' However, if I tried to do this instead:
s = {}
s[test] = 1
I'd get a NameError exception, because this would be looking for an undefined variable called test whose value would be used as the key.
If, then, I were to type this into the Python interpreter:
>>> s = {}
>>> s['test'] = 1
>>> s['othertest'] = 2
>>> test = 'othertest'
>>> print s[test]
2
>>> print s['test']
1
you'll see that using test as a key with no quotes uses the value of that variable to look up the associated entry in the dictionary s.
Edit: Now, the REALLY interesting question is why using s[id] gave you what you expected. The keyword "id" is actually a built-in function in Python that gives you a unique id for an object passed as its argument. What in the world the Python interpreter is doing with the expression s[id] is a total mystery to me.
Edit 2: Watching the OP's Youtube video, it's clear that he's staying consistent when assigning and reading the hash about using id or 'id', so there's no issue with the function id as a hash key somehow magically lining up with 'id' as a hash key. That had me kind of worried for a while.