Conventions and Grammar versions in Python
View more Tutorials:
Like other languages, Python has some naming conventions such as naming rules of variable, function, class, module,...
A name can begin with capital letters (A-Z), or lowercase ones (a-z), or undercore (_), followed by other letters or nothing.
Python does not accept the characters: @, $ and % in the name.
Python is a programming language that distinguishes between uppercase and lowercase, MyObject and myobject are two different ones.
Python does not accept the characters: @, $ and % in the name.
Python is a programming language that distinguishes between uppercase and lowercase, MyObject and myobject are two different ones.
Some naming rules in Python:
- Class name should begin with a capital letter, other names should begin with lowercase ones.
- A name begins with an underscore, it means that the name is private.
- A name begins with two underscores, it means that the name is very private.
- If a name bigins with two underscores and ends with two underscores, it means the name is special one that has already defined by Python.
There are a few the keywords in Python which can not be used to name and has no capital letters. Below is list of all the keywords in Python.
** keywords **
and assert break class continue def del elif else except exec finally for from global if import in is lambda not or pass raise return try yield while
List of special words:
** special words **
None True False self cls class_
The common functions:
** func **
__import__ abs all any apply basestring bin bool buffer callable chr classmethod cmp coerce compile complex delattr dict dir divmod enumerate eval execfile file filter float format frozenset getattr globals hasattr hash help hex id input int intern isinstance issubclass iter len list locals long map max min next object oct open ord pow print property range raw_input reduce reload repr reversed round set setattr slice sorted staticmethod str sum super tuple type type unichr unicode vars xrange zip
Unlike other programming languages, Python does not use the pairs of keywords such as “begin” and “end” or “{” và “}” to open or close a block statements. Instead, Python makes rules that sequential statements having the same line indentation belongs in the same block.
if True:
print ("Hello")
print ("True")
else:
print ("False")
You will get error report if you do it as below:
The rule of writing a statement on multiple lines:
Normally, a statement of Python will be written in 1 line, and a line break means the end of that statement. However, there are long statement that you want to write them on multiple lines, you need to inform Python of your intent. Let's use symbol \ to inform Python that the statement includes the next line. For example:
value = 1 + \
2 + \
3
The rules of writing multiple statements on a line
You can write multiple statements on a line, you need to use a semicolon (;) to separate them. For example:
a = 'One'; b = "Two"; c ="Three"
Python allows you to use single quotes ('), or double quotes (") to denote a string on a line:
str1 = 'Hello every body' str2 = "Hello Python"
If a string is written on multiple lines, you need to use a pair of 3 quotes (And not use \):
multiLineStr = """This is a paragraph. It is
made up of multiple lines and sentences."""
The sharp character (#) not being in the string will begin with a comment line.
All the characters behind it until the end of line are considered a part of the comment, and the Python interpreter will ignore them when running the program.
All the characters behind it until the end of line are considered a part of the comment, and the Python interpreter will ignore them when running the program.
# First comment
print ("Hello, Python!") # second comment
# This is a comment.
# This is a comment, too.
# This is a comment, too.
print ("Finish")
Currently, the latest version of Python is 3.x, Python 3.x has some stricter rules of grammar compared to Python 2.x, most the Python current documents on Internet are using Grammar 2.x and it can confuse you because you have carried out according to the guide but still getting error report.
Example:
In order to print out on the screen with the words "Hello World", for the version 2.x you need to use the "print" statement without round brackets ( ):
# Grammar Python 2.x print "Hello World"
For the Python 3.x grammar, in order to print out the words "Hello World", you have to put it into round brackets ( ), or you will get error report.
# Grammar Python 3.x
print ("Hello World")
Therefore, when you create a project, you need to specify which the grammar version you use. The example below illustrates "Create a project" on Eclipse, and specifies "Python Grammar" version 3.6.
