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Okay. So my question is simple: How can I assign the value of a variable using eval in Python? I tried eval('x = 1') but that won't work. It returns a SyntaxError. Why won't this work?
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You can use the built-in Python eval() to dynamically evaluate expressions from a string-based or compiled-code-based input. If you pass in a string to eval() , then the function parses it, compiles it to bytecode, and evaluates it as a Python expression.
The assignment operator, denoted by the “=” symbol, is the operator that is used to assign values to variables in Python. The line x=1 takes the known value, 1, and assigns that value to the variable with name “x”. After executing this line, this number will be stored into this variable.
Answer: eval is a built-in- function used in python, eval function parses the expression argument and evaluates it as a python expression. In simple words, the eval function evaluates the “String” like a python expression and returns the result as an integer.
In this program, expression can have sqrt() method and variable a only. All other methods and variables are unavailable. Restricting the use of eval() by passing globals and locals dictionaries will make your code secure particularly when you are using input provided by the user to the eval() method.
Because x=1 is a statement, not an expression. Use exec to run statements.
>>> exec('x=1') >>> x 1 By the way, there are many ways to avoid using exec/eval if all you need is a dynamic name to assign, e.g. you could use a dictionary, the setattr function, or the :locals() dictionary
>>> locals()['y'] = 1 >>> y 1 Update: Although the code above works in the REPL, it won't work inside a function. See Modifying locals in Python for some alternatives if exec is out of question.
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You can't, since variable assignment is a statement, not an expression, and eval can only eval expressions. Use exec instead.
Better yet, don't use either and tell us what you're really trying to do so that we can come up with a safe and sane solution.
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