Jul 8, 2010 · The rule of thumb for repr is that if it makes sense to return Python code that could be evaluated to produce the same object, do that, just like str, frozenset, and most other builtins do, but if it doesn't, use the angle-bracket form to make sure that what you return can't possibly be mistaken for a human-readable-and-evaluatable-as-source repr.

Feb 3, 2012 · You're confusing the variable name with the string of the animal name: In here: cat = 7 cat is the variable, 7 its value. In: cat = 'cat' cat is still the variable and 'cat' is the string with the animal name. You can put whatever string you like inside cat even cat = 'dog'.

This is obviously clunkier than just calling .format on the string; the motivation is to allow users to subclass Formatter to define a different syntax for the template string. All of the above approaches use a common "formatting language" (although string.Formatter allows changing it); there are many other things that can be put inside the {} .

Even in the very rare cases where you do have a good reason to dynamically create a variable, this is not the way to do it; just use setattr. And even when setattr is inappropriate for whatever reason, being explicit and modifying locals or globals as appropriate is still better than exec .

See Format String Syntax for a description of the various formatting options that can be specified in format strings. This method of string formatting is the new standard in Python 3.0, and should be preferred to the % formatting described in String Formatting Operations in new code. New in …

The reason it doesn't work, at least on CPython, is that CPython allocates a fixed size array for locals, and the size of said array is determined when the function is defined, not when its run, and can't be changed (access to true locals doesn't even use the name; the name is replaced with the index into the array at function compile time).

Jul 19, 2012 · I have a variable with a string assigned to it and I want to define a new variable based on that string. foo = "bar" foo = "something else" # What I actually want is: bar...

Aug 25, 2013 · def getVariableName(variable, globalVariables=globals().copy()): """ Get Variable Name as String by comparing its ID to globals() Variables' IDs args: variable(var): Variable to find name for (Obviously this variable has to exist) kwargs: globalVariables(dict): Copy of the globals() dict (Adding to Kwargs allows this function to work properly ...

Oct 7, 2009 · The method globals().items() returns a list of tuples; in each tuple the first item is the variable name (as a string) and the second is the variable value. My variablename() function searches through that list to find the variable name(s) that corresponds to the value of the variable whose name I need in string form.

Apr 12, 2012 · You can use Python 3.6's f-strings for variables inside multi-line or lengthy single-line strings. You can manually specify newline characters using \n.