| 1 | # This program is public domain |
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| 2 | """ |
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| 3 | @organization: Module loader contains class Loader which uses |
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| 4 | some readers to return values contained in a file readed. |
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| 5 | |
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| 6 | """ |
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| 7 | import imp,os,sys |
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| 8 | import logging |
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| 9 | import os.path |
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| 10 | logging.basicConfig(level=logging.ERROR, |
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| 11 | format='%(asctime)s %(levelname)s %(message)s', |
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| 12 | filename='test_log.txt', |
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| 13 | filemode='w') |
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| 14 | |
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| 15 | def _findReaders(dir): |
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| 16 | # List of plugin objects |
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| 17 | plugins = [] |
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| 18 | # Go through files in plug-in directory |
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| 19 | try: |
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| 20 | |
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| 21 | list = os.listdir(dir) |
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| 22 | for item in list: |
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| 23 | |
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| 24 | toks = os.path.splitext(os.path.basename(item)) |
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| 25 | if toks[1]=='.py' and not toks[0]=='__init__': |
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| 26 | name = toks[0] |
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| 27 | path = [os.path.abspath(dir)] |
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| 28 | file = None |
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| 29 | try: |
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| 30 | (file, path, info) = imp.find_module(name, path) |
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| 31 | module = imp.load_module( name, file, item, info ) |
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| 32 | if hasattr(module, "Reader"): |
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| 33 | try: |
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| 34 | plugins.append(module.Reader()) |
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| 35 | except: |
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| 36 | logging.error("Error accessing Reader in %s\n %s" % (name, sys.exc_value)) |
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| 37 | except : |
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| 38 | logging.error("Error importing %s\n %s" % (name, sys.exc_value)) |
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| 39 | finally: |
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| 40 | if not file==None: |
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| 41 | file.close() |
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| 42 | except: |
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| 43 | # Should raise and catch at a higher level and display error on status bar |
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| 44 | pass |
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| 45 | return plugins |
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| 46 | |
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| 47 | |
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| 48 | class Loader(object): |
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| 49 | """ |
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| 50 | Loader class extracts data from a given file. |
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| 51 | This provides routines for opening files based on extension, |
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| 52 | and readers built-in file extensions. |
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| 53 | It uses functionalities for class Load |
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| 54 | @note: For loader to operate properly each readers used should |
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| 55 | contain a class name "Reader" that contains a field call ext. |
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| 56 | Can be used as follow: |
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| 57 | L=Loader() |
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| 58 | self.assertEqual(l.__contains__('.tiff'),True) |
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| 59 | #Recieves data |
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| 60 | data=L.load(path) |
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| 61 | """ |
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| 62 | #Store instance of class Load |
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| 63 | __load = None |
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| 64 | |
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| 65 | |
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| 66 | class Load(object): |
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| 67 | |
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| 68 | def __init__(self): |
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| 69 | #Dictionary containing readers and extension as keys |
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| 70 | self.readers = {} |
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| 71 | #Load all readers in plugins |
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| 72 | self.__setitem__() |
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| 73 | |
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| 74 | |
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| 75 | def __setitem__(self,dir=None, ext=None, reader=None): |
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| 76 | """ |
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| 77 | __setitem__ sets in a dictionary(self.readers) a given reader |
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| 78 | with a file extension that it can read. |
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| 79 | @param ext: extension given of type string |
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| 80 | @param reader:instance Reader class |
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| 81 | @param dir: directory name where plugins readers will be saved |
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| 82 | @raise : ValueError will be raise if a "plugins" directory is not found |
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| 83 | and the user didn't add a reader as parameter or if the user didn't |
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| 84 | add a reader as a parameter and plugins directory doesn't contain |
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| 85 | plugin reader. |
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| 86 | if an extension is not specified and a reader does not contain a field |
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| 87 | ext , a warning is printed in test_log.txt file. |
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| 88 | @note: when called without parameters __setitem__ will try to load |
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| 89 | readers inside a "readers" directory |
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| 90 | if call with a directory name will try find readers |
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| 91 | from that directory "dir" |
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| 92 | """ |
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| 93 | if dir==None: |
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| 94 | dir = 'readers' |
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| 95 | dir=os.path.join(os.path.dirname(os.path.abspath(__file__)),dir) |
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| 96 | |
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| 97 | if (reader==None and ext==None) or dir:#1st load |
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| 98 | plugReader=None |
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| 99 | if os.path.isdir(dir): |
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| 100 | plugReader=_findReaders(dir)# import all module in plugins |
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| 101 | if os.path.isdir('../'+dir): |
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| 102 | plugReader=_findReaders('../'+dir) |
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| 103 | |
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| 104 | |
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| 105 | if plugReader !=None: |
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| 106 | list=[] |
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| 107 | for preader in plugReader:# for each modules takes list of extensions |
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| 108 | try: |
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| 109 | list=preader.ext |
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| 110 | except AttributeError,msg: |
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| 111 | logging.warning(msg) |
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| 112 | pass |
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| 113 | #raise AttributeError," %s instance has no attribute 'ext'"\ |
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| 114 | #%(preader.__class__) |
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| 115 | if list !=[]: |
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| 116 | for item in list: |
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| 117 | ext=item |
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| 118 | if ext not in self.readers:#assign extension with its reader |
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| 119 | self.readers[ext] = [] |
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| 120 | self.readers[ext].insert(0,preader) |
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| 121 | #Reader and extension are given |
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| 122 | elif reader !=None and ext !=None: |
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| 123 | if ext not in self.readers: |
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| 124 | self.readers[ext] = [] |
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| 125 | self.readers[ext].insert(0,reader) |
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| 126 | elif reader!=None: |
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| 127 | #only reader is receive try to find a field ext |
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| 128 | try: |
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| 129 | list=preader.ext |
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| 130 | except: |
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| 131 | raise AttributeError," Reader instance has no attribute 'ext'" |
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| 132 | for item in list: |
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| 133 | |
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| 134 | ext=item |
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| 135 | if ext not in self.readers:#assign extension with its reader |
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| 136 | self.readers[ext] = [] |
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| 137 | self.readers[ext].insert(0,reader) |
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| 138 | |
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| 139 | else: |
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| 140 | raise ValueError,"missing reader" |
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| 141 | |
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| 142 | |
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| 143 | def __getitem__(self, ext): |
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| 144 | """ |
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| 145 | __getitem__ get a list of readers that can read a file with that extension |
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| 146 | @param ext: file extension |
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| 147 | @return self.readers[ext]:list of readers that can read a file |
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| 148 | with that extension |
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| 149 | """ |
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| 150 | return self.readers[ext] |
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| 151 | |
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| 152 | def __contains__(self, ext): |
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| 153 | """ |
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| 154 | @param ext:file extension |
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| 155 | @return: True or False whether there is a reader file with that extension |
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| 156 | """ |
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| 157 | return ext in self.readers |
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| 158 | |
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| 159 | |
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| 160 | def formats(self, name=True, ext=False): |
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| 161 | """ |
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| 162 | Return a list of the registered formats. If name=True then |
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| 163 | named formats are returned. If ext=True then extensions |
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| 164 | are returned. |
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| 165 | """ |
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| 166 | names = [a for a in self.readers.keys() if not a.startswith('.')] |
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| 167 | exts = [a for a in self.readers.keys() if a.startswith('.')] |
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| 168 | names.sort() |
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| 169 | exts.sort() |
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| 170 | ret = [] |
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| 171 | if name: ret += names |
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| 172 | if ext: ret += exts |
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| 173 | return ret |
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| 174 | |
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| 175 | def lookup(self, path): |
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| 176 | """ |
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| 177 | Return the loader associated with the file type of path. |
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| 178 | """ |
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| 179 | file = os.path.basename(path) |
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| 180 | idx = file.find('.') |
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| 181 | ext = file[idx:] if idx >= 0 else '' |
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| 182 | |
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| 183 | try: |
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| 184 | return self.readers[ext] |
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| 185 | except: |
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| 186 | logging.warning("Unknown file type '%s'"%ext) |
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| 187 | raise RuntimeError, "Unknown file type '%s'"%ext |
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| 188 | |
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| 189 | |
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| 190 | |
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| 191 | def load(self, path, format=None): |
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| 192 | """ |
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| 193 | Call reader for the file type of path. |
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| 194 | @param path: path to file to load |
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| 195 | @param format: extension of file to load |
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| 196 | @return Data if sucessful |
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| 197 | or None is not reader was able to read that file |
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| 198 | Raises ValueError if no reader is available. |
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| 199 | May raise a loader-defined exception if loader fails. |
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| 200 | """ |
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| 201 | try: |
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| 202 | os.path.isfile( os.path.abspath(path)) |
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| 203 | except: |
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| 204 | raise ValueError," file path unknown" |
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| 205 | |
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| 206 | if format is None: |
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| 207 | try: |
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| 208 | readers = self.lookup(path) |
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| 209 | except ValueError,msg: |
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| 210 | raise ValueError,str(msg) |
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| 211 | else: |
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| 212 | readers = self.readers[format] |
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| 213 | if readers!=None: |
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| 214 | for fn in readers: |
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| 215 | try: |
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| 216 | value=fn.read(path) |
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| 217 | return value |
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| 218 | except ValueError,msg: |
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| 219 | logging.error(str(msg)) |
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| 220 | else: |
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| 221 | raise ValueError,"Loader contains no reader" |
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| 222 | |
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| 223 | |
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| 224 | def __init__(self): |
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| 225 | """ Create singleton instance """ |
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| 226 | # Check whether we already have an instance |
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| 227 | if Loader.__load is None: |
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| 228 | # Create and remember instance |
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| 229 | Loader.__load = Loader.Load() |
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| 230 | Loader.__load.__setitem__() |
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| 231 | # Store instance reference as the only member in the handle |
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| 232 | self.__dict__['_Loader__load'] = Loader.__load |
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| 233 | |
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| 234 | def __getattr__(self, attr): |
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| 235 | """ Delegate access to implementation """ |
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| 236 | return getattr(self.__load, attr) |
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| 237 | |
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| 238 | def __setattr__(self, attr, value): |
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| 239 | """ Delegate access to implementation """ |
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| 240 | return setattr(self.__load, attr, value) |
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