What is Python
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Python is high-level dynamically typed interpreted programming language. Its design philosophy emphasizes code readability, and its syntax allows programmers to express concepts in fewer lines of code than would be possible in languages such as C++ or Java.
There should be one — and preferably only one — obvious way to do it
Universality - general purpose:
Machine Learning, Web, Testing, services, game logic, math, science, education
except DBs and things that required super fast computing
The programming language Python was conceived in the late 1980s
Implementation was started in December 1989 by Guido van Rossum at CWI in the Netherlands.
Python was named for the BBC TV show Monty Python's Flying Circus.
Python 1.0 was released on January 1994.
Python 2.0 was released on October 2000.
Python 3.0 was released on December 2008.
Guido van Rossum is Python's principal author, and his continuing central role in deciding the direction of Python is reflected in the title given to him by the Python community, Benevolent Dictator for Life (BDFL).
In July 2018, van Rossum announced that he would be stepping down from the position of BDFL of the Python programming language. Many thinks that's why:
"Now that PEP 572 is done, I don't ever want to have to fight so hard for a PEP and find that so many people despise my decisions."
Worked at:
Dropbox
Microsoft
First commit to SVN:
Versions:
Python 1.0 was released on January 1994.
Python 2.0 was released on October 16, 2000, with many major new features, including a cycle-detecting garbage collector (in addition to reference counting) for memory management and support for Unicode.
Python 3.0, a major, backwards-incompatible release, was released on December 3, 2008 after a long period of testing. Many of its major features have also been backported to the backwards-compatible Python 2.6 and 2.7.
In 2022, Python 3.10.4 and 3.9.12 were expedited and so were older releases including 3.8.13, and 3.7.13 because of many security issues. Python 3.9.13 is the latest 3.9 version, and from now on 3.9 (and older; 3.8 and 3.7) will only get security updates.
Full history is described in Wikipedia
Python is used in these three areas the most now:
Data Science and Machine Learning
Web Programming
Testing
Readability and indentations
Understandable tracebacks
Pretty fast for it's tasks - web, UI, math, analyse (PyPy, Cython, numpy, scipy)
Community (for FullStackOverflow developers)
Ducktyping
Tons of packages
* Ducktyping - some common behavior of different object.
No JIT
In Python code is executed after pre-compilation (bytecode creation)
Not fast compared to C, Rust, Java, Go and more memory-hungry
Python object realization is costly
Problems with concurrency (Global Interpreter Lock)
Problems with sandboxing
🔥
Python is Dynamically Typed rather than Statically Typed.
Python is interpreted rather than compiled. A smart compiler can look ahead and optimize for repeated or unneeded operations, which can result in speed-ups
Python's object model can lead to inefficient memory access
Java
Python programs are generally expected to run slower than Java programs, but they also take much less time to develop. Python programs are typically 3-5 times shorter than equivalent Java programs. This difference can be attributed to Python's built-in high-level data types and its dynamic typing. For example, a Python programmer wastes no time declaring the types of arguments or variables, and Python's powerful polymorphic list and dictionary types, for which rich syntactic support is built straight into the language, find a use in almost every Python program. Because of the run-time typing, Python's run time must work harder than Java's. For example, when evaluating the expression a+b, it must first inspect the objects a and b to find out their type, which is not known at compile time. It then invokes the appropriate addition operation, which may be an overloaded user-defined method.
C++
Almost everything said for Java also applies for C++, just more so: where Python code is typically 3-5 times shorter than equivalent Java code, it is often 5-10 times shorter than equivalent C++ code! Anecdotal evidence suggests that one Python programmer can finish in two months what two C++ programmers can't complete in a year. Python shines as a glue language, used to combine components written in C++.
There are two main branches of Python:
Python 2 (~ 2.7.17)
The old branch with the support stopped at January 2020.
Python 3 (~ 3.11)
Python 3 is a "big hotfix" for a lot of different issues found in Python 2 over the years.
Python 3 is the only current version of Python. Python 2 is almost dead and while it still can be found pre-installed on some OS distributions (Linux and Mac OSX) it will be replaced by Python 3 as the new default everywhere.
Differences are not so big in general syntax. It looks almost identical to Python 2. The most noticable change is that print is a function in Python 3, so it requires a parentheses surrounding the arguments.
print
print()
empty line ( or \r)
print "Hi!"
print("Hi!")
Hi!
print "Hi!",
print(" Hi! ", end="")
Hi! (no at the end)
print "2 + 2 =", 2+2
print("2 + 2 =", 2*2)
2 + 2 = 4
N/A
print(1, 2, 3, sep="--")
1--2--3 (with seperator)
Additionally:
Many methods don't return lists (results are iterators now):
dict.keys(), dict.items(), dict.values()
map(), filter(), zip()
range() = xrange() from Python 2
Iterator protocol change: next() -> __next__()
str = unicode
Different types objects comparison (you can't compare str and int)
PEP8 fixes
Bonus:
Annotations (used for visualizing code and for data classes in Python 3.7)
Cool unpacking:
New super() – you don't need to write what class to extend (we'll learn about them in OOP section)
Asyncio (versions 3.4, 3.5+)
String interpolations (3.6+)
Data classes (3.7+)
Interpreter - mean it runs code almost "live"
Downloadable from https://www.python.org/
Compiled code is auto-created and stored in .pyc files (for Python 3 they are in separate __pycache__ directory)
Running Python
Installation covered later
Interactive shell (UNIX/Windows):
Type commands line by line and see the results immediately
Run script (stored in a text file with .py extension):
Run an inline script:
Running a specific module:
Has this license plate:
Python is script language but still it compiles runtime code in a form of so called bytecode which Python Virtual Machine (PVM) runs (just like Java does with it's JVM):
