Python Penetration Testing Cookbook
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Key differences between Python 2.7 and Python 3

Here are some main differences between Python 2.x and Python 3:

  • Print: In Python 2, print is a statement. So, there is no need to wrap the text in parentheses for printing. But in Python 3 print is a function. So, you have to pass the string you need to print to the function in parentheses.
  • Integer pision: Python 2 considers numbers without any digits after the decimal point as integers, which may lead to some unexpected results during pision.
  • List comprehension loop variables leak: In Python 2, giving the variable that is iterated over in a list comprehension leaks the variable into surrounding scope, this list comprehension loop variable leak bug has been fixed in Python 3.
  • Unicode strings: Python 2 requires you to mark the unicode string explicitly with the u prefix. But, Python 3 stores strings as unicode by default.
  • Raising exceptions: Python 3 requires different syntax for raising exceptions.

The progression from Python 2.x to Python 3.x is happening slowly, but it is underway. It is good to be mindful that there are material differences between Python 2.x and Python 3 as you may need to deal with code that is written in the version with which you are less familiar.