Python
Pyhton2 vs Python3
There is more than one Python There are two main kinds of Python, called Python 2 and Python 3.
Python 2 is an older version of the original Python. Its development has since been intentionally stalled, although that doesn't mean that there are no updates to it. On the contrary, the updates are issued on a regular basis, but they are not intended to modify the language in any significant way. They rather fix any freshly discovered bugs and security holes. Python 2's development path has reached a dead end already, but Python 2 itself is still very much alive.
Python 3 is the newer (or to be more precise, the current) version of the language. It's going through its own evolutionary path, creating its own standards and habits.
These two versions of Python aren't compatible with each other. Python 2 scripts won't run in a Python 3 environment and vice versa, so if you want the old Python 2 code to be run by a Python 3 interpreter, the only possible solution is to rewrite it, not from scratch, of course, as large parts of the code may remain untouched, but you do have to revise all the code to find all possible incompatibilities. Unfortunately, this process cannot be fully automatized.
It's too hard, too time-consuming, too expensive, and too risky to migrate an old Python 2 application to a new platform, and it's even possible that rewriting the code will introduce new bugs into it. It's easier, and more sensible, to leave these systems alone and to improve the existing interpreter, instead of trying to work inside the already functioning source code.
Python 2 vs. Python 3 conceptPython 3 isn't just a better version of Python 2 – it is a completely different language, although it's very similar to its predecessor. When you look at them from a distance, they appear to be the same, but when you look closely, though, you notice a lot of differences.
If you're modifying an old existing Python solution, then it's highly likely that it was coded in Python 2. This is the reason why Python 2 is still in use. There are too many existing Python 2 applications to discard it altogether.
Compilation vs. interpretation
Computer programming is the act of composing the selected programming language's elements in the order that will cause the desired effect. The effect could be different in every specific case – it's up to the programmer's imagination, knowledge and experience.
COMPILATION
the source program is translated once (however, this act must be repeated each time you modify the source code) by getting a file (e.g., an .exe file if the code is intended to be run under MS Windows) containing the machine code; now you can distribute the file worldwide; the program that performs this translation is called a compiler or translator;
INTERPRETATION
you (or any user of the code) can translate the source program each time it has to be run; the program performing this kind of transformation is called an interpreter, as it interprets the code every time it is intended to be executed; it also means that you cannot just distribute the source code as-is, because the end-user also needs the interpreter to execute it.
What does the interpreter actually do?
The interpreter reads the source code in a way that is common in Western culture: from top to bottom and from left to right. There are some exceptions - they'll be covered later in the course.
The interpreter will inform you where the error is located and what caused it. However, these messages may be misleading, as the interpreter isn't able to follow your exact intentions, and may detect errors at some distance from their real causes.
Python is an interpreted language. This means that it inherits all the described advantages and disadvantages. Of course, it adds some of its unique features to both sets.
If you want to program in Python, you'll need the Python interpreter. You won't be able to run your code without it. Fortunately, Python is free. This is one of its most important advantages.
Tips and Tricks
Iterate with enumerate() instead of range(len())
Use List Comprehension instead of raw for loops
Sort complex iterables with sorted() - This sorts the numbers in a new list ordered correctly:
For decending order:
For sorting a List of dictionaries afer age:
Store Unique values with Sets: If you need to get the uique values: - NO DUPLICATES
Save Memory with Generators First Example uses a list to generate all the values and then adds them together (This one uses "[ ]") The second example generates one item at a time (This one users "( )")
Define default values in Dictionaries with .get() and .setdefault()
Count hashable objects with collections.Counter
Last updated