Python Syntax

Python syntax consists of a set of rules which are used to make Python Programs. This Python Programming language syntax has several similarities with the Perl, Java, and C Programming languages.

Moreover,this tutorial will guide you on the execution of the Python program to Print “Hello World” in the 2 different modes of Python programming. It will also discuss the Python reserved codes.

What is Python Syntax?

Python syntax is considered as the set of rules that will further define a combination of symbols, which is required to write the structured programs of Python correctly.

Furthermore, these rules are defined to ensure that programs are written in Python and must be structured and formatted. Thus, the Python Interpreter can analyze and run the program accurately.

How to execute the first Python Program?

Python Programs can be executed for printing “Hello World” in two different modes of Python Programming. These are a) Interactive Mode Programming and b) Script Mode Programming.

Python- Interactive Mode Programming

Python interpreter can be brought up from the command line by entering Python in the command prompt as provided below:

$ python3
Python 3.10.6 (main, Mar 10 2023, 10:55:28) [GCC 11.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

In this command prompt, >>> represents a Python Command Prompt and the command can be entered. The following text can be entered at the Python Prompt and then, select enter.

>>> print ("Hello, World!")

However, it is required to print a statement without parenthesis as in the print “Hello, World!”. If you are using the old version of Python like Python 2.4x. The output in Python version 3. x will be the following:

Hello, World!

What is Python-Script Mode Programming?

Python Interpreter can be brought up with the script parameter which has an execution of the script and will be continued until the script is completed. Thus, the interpreter won’t be available when the script is completed.

To write a simple Python Program, where the Python Program has an extension of .py. Enter the following code in the test.py file.

print ("Hello, World!")

Suppose you have an interpreter path that is set in a Path Variable. Run the program that is given below:

$ python3 test.py

The desired output is the following:

Hello, World!

Another way to execute the Python script is provided here. The modified test.py file is the following

#!/usr/bin/python3

print ("Hello, World!")

Suppose the interpreter will be accessible in the /usr/bin directory. Run the program given below:

$ chmod +x test.py     # This is to make file executable
$./test.py

The desired result is the following:

Hello, World!

What is a Python Identifier?

Python identifier refers to identifying a variable, function, class, module, and other object. An identifier will begin with the letter A to Z which is followed by zero, underscores, and digits.

Python won’t allow any punctuation characters like  @, $, and %  within the identifiers.

The criteria for naming the Python identifiers are the follows:

a. Python Class name will start with the uppercase letter. All the other identifiers will start with a lowercase letter.

b. An identifier will start with the single leading underscore that will refer to the identifier as private.

c. Identifier which begins with the two leading underscores will show that it has a strongly private identifier.

d. The identifier will end up with the two trailing underscores and also, the identifier has a language-defined special name.

What are the Python Keywords?

Python Keywords are reserved words and can’t be used as constants or variables. The Python Keyword must have lowercase letters.

and	as	assert
break	class	continue
def	del	elif
else	except	False
finally	for	from
global	if	import
in	is	lambda
None	nonlocal	not
or	pass	raise
return	True	try
while	with	yield

What are Python Lines and Indentation?

Python Programming has no braces for representing the block of code for class and function definitions. The block of code is represented by line indentation.

However, the number of spaces in indentation is considered as a variable. Whereas, all the statements within the block will be indented in the same way. Let’s check the example provided below:

if True:
   print ("True")
else:
   print ("False")

The block given below has an error

if True:
   print ("Answer")
   print ("True")
else:
   print ("Answer")
   print ("False")

It’s important to remember that the continuous lines that are intended with the same number of spaces can create a block. The example given below will illustrate the several statement blocks:

import sys

try:
   # open file stream
   file = open(file_name, "w")
except IOError:
   print "There was an error writing to", file_name
   sys.exit()
print "Enter '", file_finish,
print "' When finished"
while file_text != file_finish:
   file_text = raw_input("Enter text: ")
   if file_text == file_finish:
      # close the file
      file.close
      break
   file.write(file_text)
   file.write("\n")
file.close()
file_name = raw_input("Enter filename: ")
if len(file_name) == 0:
   print "Next time please enter something"
   sys.exit()
try:
   file = open(file_name, "r")
except IOError:
   print "There was an error reading file"
   sys.exit()

What is Python Multi-Line Statements?

Python Statements will mostly end with a new line. So, python will use the line continuation character / to show that the line will continue. Refer to the example given below:

total = item_one + \
        item_two + \
        item_three

The statements that are enclosed with the  [], {}, or ()  brackets will use the line continuation character. The following example will work in Python:

days = ['Monday', 'Tuesday', 'Wednesday',
        'Thursday', 'Friday']

What is Quotations in Python ?

Python will accept single (‘), double (“), and triple (”’ or ” “)  for representing the string literals. We know that the same type of quote will start and end with the same string type.

The triple quotes are mostly used for the multiple lines. Let us check the example given below.

word = 'word'
print (word)

sentence = "This is a sentence."
print (sentence)

paragraph = """This is a paragraph. It is
 made up of multiple lines and sentences."""
print (paragraph)

What is Comments in Python?

A comment is referred to as a programmer-readable explanation in the Python source code. So, comments are mostly added to the source code for easier readability. It will be neglected by the Python interpreter.

Python will have single-line and multi-line comments. Python comments are mostly similar to the comments that are available in the PHP, BASH, and Perl Programming languages.

A hash sign (#) that is not kept inside a string will denote the beginning of a comment. Every character will have # from the start to the end of the physical line and so the Python interpreter will neglect this comment.

# First comment
print ("Hello, World!") # Second comment

The result is provided below:

Hello, World!

Enter the comment on the same line after the statement

name = "Madisetti" # This is again comment

Type the multiple lines comment as the following:

# This is a comment.
# This is a comment, too.
# This is a comment, too.
# I said that already.

However, the triple quoted string will be neglected by the Python interpreter and thus will denote the multi-line comments.

'''
This is a multiline
comment.
'''

Using Black Lines in Python Programs

A line consists of a whitespace which can include a comment and is known as a black line and the Python interpreter will ignore it.

Whereas, you are required to enter the empty physical line to end the multiline statement in an interactive interpreter session.

Waiting for a User

The program that is provided below will denote the prompt and the statement will tell to “Press the enter key to exit” and then wait to take the required action by the user.

#!/usr/bin/python

raw_input("\n\nPress the enter key to exit.")

In the program given above, “\n\n” will make two new lines before showing the actual line. After the user clicks the key, the program will automatically stop.

Multi Statements Groups as Suites

The group of individual statements will make a single code block which is referred to as a suite in Python. Compound or complex sentences like the if, while, def, and class. It will need a header line and a suite.

Header lines will start with the statement with the keyword and then will end with the colon (: ). This will have one or more lines that can create a suite.

if expression :
   suite
elif expression :
   suite
else :
   suite

What is Command Line Arguments in Python?

Several Programs can be executed with a few basic information about the program being executed. This can be done using the -h-

$ python3 -h
usage: python3 [option] ... [-c cmd | -m mod | file | -] [arg] ...
Options and arguments (and corresponding environment variables):
-c cmd : program passed in as string (terminates option list)
-d     : debug output from parser (also PYTHONDEBUG=x)
-E     : ignore environment variables (such as PYTHONPATH)
-h     : print this help message and exit

[ etc. ]

It is also possible to script the program in a manner that has several options.

Conclusion

To conclude, this article will allow the students to understand how to execute the Python program along with the examples. This illustrated example will allow them to know more about this. Adding the comments in the Python program is also included.

Python Syntax- FAQs