Strings in Python - Part 1

Besides numbers, Python can also manipulate strings, which can be expressed in several ways. They can be enclosed in single quotes ('...') or double quotes ("...") with the same result. \ can be used to escape quotes.

In the interactive interpreter, the output string is enclosed in quotes and special characters are escaped with backslashes. While this might sometimes look different from the input (the enclosing quotes could change), the two strings are equivalent. 

The string is enclosed in double quotes if the string contains a single quote and no double quotes, otherwise it is enclosed in single quotes. The print() function produces a more readable output, by omitting the enclosing quotes and by printing escaped and special characters.

If you don’t want characters prefaced by \ to be interpreted as special characters, you can use raw strings by adding an r before the first quote.

Using Python as a Calculator

Numbers

The interpreter acts as a simple calculator.

We can type an expression at it and it will write the value. Expression syntax is straightforward.

The operators +, -, * and / work just like in most other languages (like Pascal or C).

Parentheses (()) can be used for grouping.

Division (/) always returns a float.

It is possible to use the ** operator to calculate powers.

The equal sign (=) is used to assign a value to a variable.

If a variable is not “defined” (assigned a value), trying to use it will give you an error.

There is full support for floating point; operators with mixed type operands convert the integer operand to floating point.

In interactive mode, the last printed expression is assigned to the variable _. This means that when you are using Python as a desk calculator, it is somewhat easier to continue calculations.

Comments in Python

The examples given in this blog, input and output are distinguished by the presence or absence of prompts (>>> and ...) : to repeat the example, you must type everything after the prompt, when the prompt appears; lines that do not begin with a prompt are output from the interpreter. Note that a secondary prompt on a line by itself in an example means you must type a blank line; this is used to end a multi-line command.

Comments in Python start with the hash character (#) and extend to the end of the physical line. A comment may appear at the start of a line or following white-space or code, but not within a string literal. A hash character within a string literal is just a hash character. Since comments are to clarify code and are not interpreted by Python, they may be omitted when typing in examples.

How to Install Python?

Now you can go to the https://www.python.org and download the latest version of the Python.

But here I used Python 3.6.0. version. Now install the downloaded setup and then you can search it from the start menu whether is it install correctly or not.

First of all you have to go to the IDLE (Python GUI) in the start menu. Then test it via print() statement whether the IDLE is working correctly or not. Given below my output.

Python Applications

Web Applications
Python provides libraries to handle internet protocols such as HTML and XML, JSON, Email processing, request, beautifulSoup, Feedparser etc. It also provides frameworks such as Django, Pyramid, Flask etc to design and develop web based applications. PythonWikiEngines, Pocoo, PythonBlogSoftware are the important developments of Python.

Desktop GUI Applications
Python provides Tk GUI library to develop user interface in python based applications. Other toolkits like wxWidgets, Kivy, pyqt are usable to several platforms. Kivy is popular for writing multi-touch applications.

Software Development
Python works as a support language and can be used for build control management and testing etc.

Scientific and Numeric
Some useful libraries and packages are SciPy, Pandas, IPython etc. SciPy is a group of packages of engineering , science and mathematics.

Business Applications
Python is used to ERP and e-commerce systems. Tryton is a high level application platform.

Console based Applications
Python is used to develop console based applications like IPython.

Audio / Video based Applications
Some of the real multimedia applications are TimPlayer, cplay etc.

3D CAD Applications
CAD application Fandango is a real application which provides full features of CAD.

Enterprise Applications
Some real enterprise applications are OpenErp, Tryton, Picalo etc.

Applications for Images
Python used to develop applications for image such as VPython, Gogh, imgSeek etc.

Introduction to Python

Python is an easy to learn, powerful programming language. It has efficient high-level data structures and a simple but effective approach to object-oriented programming. 

Python’s elegant syntax and dynamic typing, together with its interpreted nature make it an ideal language for scripting and rapid application development in many areas on most platforms.

The Python interpreter and the extensive standard library are freely available in source or binary form for all major platforms from the Python Web site, https://www.python.org and may be freely distributed. The same site also contains distributions of and pointers to many free third party Python modules, programs and tools and additional documentation.

The Python interpreter is easily extended with new functions and data types implemented in C or C++ (or other languages callable from C). Python is also suitable as an extension language for customizable applications.

Python is simple to use, but it is a real programming language offering much more structure and support for large programs than shell scripts or batch files can offer.

Python offers much more error checking than C and being a very-high-level language, it has high-level data types built in, such as flexible arrays and dictionaries. Because of its more general data types Python is applicable to a much larger problem domain than Awk or even Perl, yet many things are at least as easy in Python as in those languages.

Python allows you to split your program into modules that can be reused in other Python programs. It comes with a large collection of standard modules that you can use as the basis of your programs or as examples to start learning to program in Python. Some of these modules provide things like file I/O, system calls, sockets and even interfaces to graphical user interface tool kits like Tk. 

Python is an interpreted language which can save you considerable time during program development because no compilation and linking is necessary. The interpreter can be used interactively, which makes it easy to experiment with features of the language to write throw-away programs or to test functions during bottom-up program development. It is also a handy desk calculator.

Python enables programs to be written compactly and readable. Programs written in Python are typically much shorter than equivalent C, C++ or Java programs for several reasons. The reasons are given below.

• The high-level data types allow you to express complex operations in a single statement.
• Statement grouping is done by indentation instead of beginning and ending brackets.
• No variable or argument declarations are necessary.

·                                                                                                                                                           Python is Extensible.

      

     If you know how to program in C it is easy to add a new built-in function or module to the interpreter, either to perform critical operations at maximum speed or to link Python programs to libraries that may only be available in binary form (such as a vendor-specific graphics library). Once you are really hooked, you can link the Python interpreter into an application written in C and use it as an extension or command language for that application.