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    <p>There is an usage scenario where you might need this. I'm not implying there are not better ways or achieving the same functionality.</p> <p>This would be useful in order to 'dump' an arbitrary list of dictionaries in case of error, in debug modes and other similar situations.</p> <p>What would be needed, is the reverse of the <code>eval()</code> function:</p> <pre><code>get_indentifier_name_missing_function() </code></pre> <p>which would take an identifier name ('variable','dictionary',etc) as an argument, and return a string containing the identifier’s name.</p> <hr> <p>Consider the following current state of affairs:</p> <pre><code>random_function(argument_data) </code></pre> <p>If one is passing an identifier name ('function','variable','dictionary',etc) <code>argument_data</code> to a <code>random_function()</code> (another identifier name), one actually passes an identifier (e.g.: <code>&lt;argument_data object at 0xb1ce10&gt;</code>) to another identifier (e.g.: <code>&lt;function random_function at 0xafff78&gt;</code>):</p> <pre><code>&lt;function random_function at 0xafff78&gt;(&lt;argument_data object at 0xb1ce10&gt;) </code></pre> <p>From my understanding, only the memory address is passed to the function:</p> <pre><code>&lt;function at 0xafff78&gt;(&lt;object at 0xb1ce10&gt;) </code></pre> <p>Therefore, one would need to pass a string as an argument to <code>random_function()</code> in order for that function to have the argument's identifier name:</p> <pre><code>random_function('argument_data') </code></pre> <p>Inside the random_function()</p> <pre><code>def random_function(first_argument): </code></pre> <p>, one would use the already supplied string <code>'argument_data'</code> to:</p> <ol> <li>serve as an 'identifier name' (to display, log, string split/concat, whatever)</li> <li><p>feed the <code>eval()</code> function in order to get a reference to the actual identifier, and therefore, a reference to the real data:</p> <pre><code>print("Currently working on", first_argument) some_internal_var = eval(first_argument) print("here comes the data: " + str(some_internal_var)) </code></pre></li> </ol> <p>Unfortunately, this doesn't work in all cases. It only works if the <code>random_function()</code> can resolve the <code>'argument_data'</code> string to an actual identifier. I.e. If <code>argument_data</code> identifier name is available in the <code>random_function()</code>'s namespace.</p> <p>This isn't always the case:</p> <pre><code># main1.py import some_module1 argument_data = 'my data' some_module1.random_function('argument_data') # some_module1.py def random_function(first_argument): print("Currently working on", first_argument) some_internal_var = eval(first_argument) print("here comes the data: " + str(some_internal_var)) ###### </code></pre> <p>Expected results would be:</p> <pre><code>Currently working on: argument_data here comes the data: my data </code></pre> <p>Because <code>argument_data</code> identifier name is not available in the <code>random_function()</code>'s namespace, this would yield instead:</p> <pre><code>Currently working on argument_data Traceback (most recent call last): File "~/main1.py", line 6, in &lt;module&gt; some_module1.random_function('argument_data') File "~/some_module1.py", line 4, in random_function some_internal_var = eval(first_argument) File "&lt;string&gt;", line 1, in &lt;module&gt; NameError: name 'argument_data' is not defined </code></pre> <hr> <p>Now, consider the hypotetical usage of a <code>get_indentifier_name_missing_function()</code> which would behave as described above.</p> <p>Here's a dummy Python 3.0 code: .</p> <pre><code># main2.py import some_module2 some_dictionary_1 = { 'definition_1':'text_1', 'definition_2':'text_2', 'etc':'etc.' } some_other_dictionary_2 = { 'key_3':'value_3', 'key_4':'value_4', 'etc':'etc.' } # # more such stuff # some_other_dictionary_n = { 'random_n':'random_n', 'etc':'etc.' } for each_one_of_my_dictionaries in ( some_dictionary_1, some_other_dictionary_2, ..., some_other_dictionary_n ): some_module2.some_function(each_one_of_my_dictionaries) # some_module2.py def some_function(a_dictionary_object): for _key, _value in a_dictionary_object.items(): print( get_indentifier_name_missing_function(a_dictionary_object) + " " + str(_key) + " = " + str(_value) ) ###### </code></pre> <p>Expected results would be:</p> <pre><code>some_dictionary_1 definition_1 = text_1 some_dictionary_1 definition_2 = text_2 some_dictionary_1 etc = etc. some_other_dictionary_2 key_3 = value_3 some_other_dictionary_2 key_4 = value_4 some_other_dictionary_2 etc = etc. ...... ...... ...... some_other_dictionary_n random_n = random_n some_other_dictionary_n etc = etc. </code></pre> <p>Unfortunately, <code>get_indentifier_name_missing_function()</code> would not see the 'original' identifier names (<code>some_dictionary_</code>,<code>some_other_dictionary_2</code>,<code>some_other_dictionary_n</code>). It would only see the <code>a_dictionary_object</code> identifier name.</p> <p>Therefore the real result would rather be:</p> <pre><code>a_dictionary_object definition_1 = text_1 a_dictionary_object definition_2 = text_2 a_dictionary_object etc = etc. a_dictionary_object key_3 = value_3 a_dictionary_object key_4 = value_4 a_dictionary_object etc = etc. ...... ...... ...... a_dictionary_object random_n = random_n a_dictionary_object etc = etc. </code></pre> <p>So, the reverse of the <code>eval()</code> function won't be that useful in this case.</p> <hr> <p>Currently, one would need to do this:</p> <pre><code># main2.py same as above, except: for each_one_of_my_dictionaries_names in ( 'some_dictionary_1', 'some_other_dictionary_2', '...', 'some_other_dictionary_n' ): some_module2.some_function( { each_one_of_my_dictionaries_names : eval(each_one_of_my_dictionaries_names) } ) # some_module2.py def some_function(a_dictionary_name_object_container): for _dictionary_name, _dictionary_object in a_dictionary_name_object_container.items(): for _key, _value in _dictionary_object.items(): print( str(_dictionary_name) + " " + str(_key) + " = " + str(_value) ) ###### </code></pre> <hr> <h2>In conclusion:</h2> <ul> <li>Python passes only memory addresses as arguments to functions.</li> <li>Strings representing the name of an identifier, can only be referenced back to the actual identifier by the <code>eval()</code> function if the name identifier is available in the current namespace.</li> <li>A hypothetical reverse of the <code>eval()</code> function, would not be useful in cases where the identifier name is not 'seen' directly by the calling code. E.g. inside any called function.</li> <li>Currently one needs to pass to a function: <ol> <li>the string representing the identifier name</li> <li>the actual identifier (memory address)</li> </ol></li> </ul> <p>This can be achieved by passing both the <code>'string'</code> and <code>eval('string')</code> to the called function at the same time. I think this is the most 'general' way of solving this egg-chicken problem across arbitrary functions, modules, namespaces, without using corner-case solutions. The only downside is the use of the <code>eval()</code> function which may easily lead to unsecured code. Care must be taken to not feed the <code>eval()</code> function with just about anything, especially unfiltered external-input data.</p>
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