Python syntax is essential for writing clean and error-free programs. It provides structure and rules that must be followed when writing Python code, and this allows the interpreter to understand the code that was written. Having a clean and readable syntax is a key reason for the popularity of Python among beginners and professional programmers. Writing proper syntax is essential for writing efficient code, which makes it easier to debug. In this article, you will explore the fundamental syntax rules of Python in detail with examples for each.
Table of Contents:
What is Syntax in Python?
Syntax in Python is a predefined set of rules that help in defining how code has to be written and structured. Syntax includes indentation, keywords, variables, and statements, among other elements that help to make the code readable and executable. Without proper syntax, errors will occur, and programming cannot be done in an efficient way. The correct syntax enables successful code execution as well as improved code organization. Understanding the syntax in Python is very important in writing clean and executable code.
Why is Syntax Important in Python?
The following are some advantages of knowing Python syntax:
- Avoids Errors: The correct syntax helps to prevent the errors that stop the execution of the program.
- Easy to Read: Python includes a syntax with plain instructions that enables readers to understand code without difficulty.
- Quick Debugging: Following the proper syntax helps in faster debugging by quickly finding the errors and resolving them.
- Works Everywhere: Proper syntax of Python makes sure that the code runs efficiently on different systems without any issues.
- Better Teamwork: Python provides a clean and consistent syntax, which makes it easy for others to understand the code and update it when required.
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Python Syntax Rules and Structure
The structure and syntax rules in Python define how the code has to be written and executed. Python has a clean and readable syntax, with proper indentation and a line structure. The syntax rules must be followed to produce a program that works correctly. Now, we will look at Python’s line structure, multiline statements, indentation, and also the rules involved in using comments and whitespaces.
1. Case Sensitivity in Python
Python treats uppercase and lowercase letters differently. This means when we use the same variable names like Var and var, both are not treated as the same.
Example:
Output:
Explanation: Here, the Python syntax treats Intellipaat and intellipaat as two different variables because variable names in Python are case-sensitive.
2. Indentation in Python
Python uses indentation, like spaces or tabs, to define code blocks instead of {} like other programming languages. The loops, functions, and conditions in Python have to be properly indented.
Example:
Output:
Explanation: Here, the print statement that is inside the function has to be indented. If the indentation is not done properly, it may raise an error.
3. Python Identifiers
Python identifiers are the names that are given to functions, classes, and objects in Python. They are very useful for identifying and referring to the elements in the Python code. Identifiers can only begin with a letter or with an underscore (_). Any special character cannot be used in the identifier except for the underscore.
Syntax:
_name = "Example"
course1 = "Example"
course_1 = "Example"
courseName = "Example"
Example:
Output:
Explanation: Here, all of the identifiers follow the Python rules, and each of them holds the name of a different course that is ultimately returned as the result.
4. Statements and Line Breaks in Python
In Python, each statement is usually typed on a new line (however, more than one statement can be typed in a single line when separated by a semicolon (;). This is generally not considered a good practice as it reduces the overall readability of the program.
Example:
Output:
Explanation: Here, the semicolon allows writing several statements in the same line, but it is mostly recommended to write each statement in a separate line to improve the readability of the code.
5. Multiline Statements in Python
If a statement is too long, backslash ‘\’ at the end of the line to split it into multiple lines, or enclose the statement within parentheses ().
Syntax:
# Using backslash
variable = "This is a long " + \
"statement"
# Using parentheses
variable = ("This is a long "
"statement")
Example:
Output:
Explanation: Here, the backslash (\) helps in breaking the long statement into multiple lines.
6. Whitespace Rules in Python
Python ignores the extra spacing except when they occurs in indentation, which will result as an error.
Some of the most important Whitespace rules are:
- Indentation: Indentation is strictly required in Python to define a block of code instead of braces { }.
- Four spaces per indentation level: This is the common method for Python and is done for readability.
- Irregular indentation: Any indentation that is not correct, e.g., adding an additional space, results in indentation issues.
- Blank lines: Adding blank lines for the comment lines that describe important logic of the code clearly helps improve the readability of the code and makes the code look neat.
Example:
Output:
Explanation: Here, spaces before or after operators do not affect execution, but incorrect indentation will cause an error.
7. Keyword Usage in Python
Python has reserved words (keywords) that cannot be used as variable names and identifiers because they are already defined and have a particular meaning that is used for performing a particular task.
| False |
class |
finally |
is |
return |
| None |
continue |
for |
lambda |
try |
| True |
def |
from |
non-local |
while |
| and |
del |
global |
not |
with |
| as |
el |
if |
or |
yield |
| assert |
else |
import |
pass |
async |
| break |
except |
in |
raise |
await |
Example:
Output:
Explanation: Here, class is a reserved keyword, so using it as a variable causes an error. Instead, a different name should be used.
8. Quotations in Python
Strings in Python are enclosed by single (‘), double (‘\’), or triple (”’ or ”’) quotes.
Example:
Output:
Explanation: Here, Python allows using different types of quotation marks, but they must be paired correctly.
9. Python Variables
The Python variables must start with a letter or an underscore(_), and they should not contain any spaces or special characters except for the underscore(_).
Rules for naming a variable in Python:
- A variable name must start with a letter (A-Z or a-z) or an underscore (_).
- It cannot start with a number (0-9).
- Only letters, digits, and underscores (_) can be used in variable names.
- No spaces and special characters (@, $, %) are allowed.
- Python is case-sensitive (name and Name are different).
- Keywords like class, def, and return cannot be used as variable names.
Syntax:
# Correct variable naming
variable_name = "Value"
Example:
Output:
Explanation: Here, variable names cannot contain special characters like ‘-‘, which leads to an error during execution, but _ is allowed as the first character.
10. Python Line Structure
Python code is composed of both physical and logical lines.
Physical line: It is a sequence of characters that ends with the line itself. Unlike C and Java, Python does not require a semicolon to indicate the conclusion of a statement.
Logical Line: A complete statement that may include one or more physical lines. Python can combine many physical lines to make a single logical line.
Syntax:
# Physical line
statement1
statement2
# Logical line using backslash (\)
variable = "Part 1 " + \
"Part 2"
Example:
Output:
Explanation: Here, each print statement is written in a separate physical line, while the variable course_name combines multiple physical lines into a single line using a ‘\’ backslash.
Exception Handling in Python
Exceptional handling in Python is used for managing the errors that occur during the execution of the program, which prevents the program from crashing unexpectedly. Python uses try, except, else, and finally for handling exceptions.
Syntax:
try:
# Code that may cause an exception
except ExceptionType:
# Code to handle the exception
else:
# Code that runs if no exception occurs
finally:
# Code that runs always
Example:
Output:
Explanation: Here, the Python code tries to print a variable that does not exist. Therefore, the except block runs and prints the error message. As an error has occurred, the else block is skipped, and the final block runs at the end.
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Control Flow Statements in Python
The control flow statements in Python help in deciding the order of execution of the code and allow repeated actions when needed.
1. Conditional Statements in Python
Conditional statements are very useful in Python because they allow the program to execute only if the condition is true. The if, elif, and else statements are used in Python for handling multiple conditions.
Syntax:
if condition1:
# Code to execute if condition1 is True
elif condition2:
# Code to execute if condition2 is True
else:
# Code to execute if none of the above conditions are True
Example:
Output:
Explanation: Here, the code first checks the if condition. If it is not true, then check the elif condition. If neither of them is true, it runs the else block.
2. Loops in Python
Loops are used for repeating a block of code multiple times. In Python, there are mainly two types of loops.
a. For Loop in Python
A for loop is used for repeating a block of code for a fixed number of times over a sequence.
Syntax:
for variable in sequence:
# code block to repeat
Example:
Output:
Explanation: Here, the loop goes through each course name that is in the course list and prints it. Each course name is printed in the same order as it is placed in the course list.
b. While Loop in Python
A while loop is used for repeating the code as long as the condition is true.
Syntax:
while condition:
# code block to repeat
Example:
Output:
Explanation: Here, the while loop starts with the count at 0 and prints each course in the list. After printing the course name, the count increases by 1, and the loop is continued till all the courses are printed.
Comments in Python are used to add explanations within the code. It helps programmers to understand the complex logic and the use of the code in a particular place. Python provides different ways to write comments, which help in increasing the readability of the code.
Some important rules to be considered while writing Python code are:
- The # must be used for single-line comments. Everything that is written after the # in the same line is ignored.
- It is important to keep the comments short and clear.
- The multi-line comments must be used only in the places where it is necessary, and the triple quotes have to be used for the long explanations.
- Adding comments to the complex code is necessary, which helps in understanding the logic.
- The comments have to be updated regularly when the code is updated.
A single-line comment starts with the # symbol. Everything after # on the same line is ignored by Python. It is usually used to give information about a single line of code.
Syntax:
# This is a single-line comment
variable = "Example"
Example:
Output:
Explanation: Here, the # symbol is used to add comments. The first comment describes the course assignment, while the second shows the printing of the course details, which consists of the name of the course along with the trainer’s name. These comments improve the readability of the program.
Python does not provide a particular syntax for multi-line comments, but multiple # symbols or triple quotes (”’ or “””) are used to write multi-line comments in Python. Triple quotes are generally used in docstring but can also act as the multiline comments.
Syntax:
# Using multiple single-line comments
# This is a comment line 1
# This is a comment line 2
# Using triple quotes
'''
This is a multi-line comment
spanning several lines
'''
Example:
Output:
Explanation: Here, triple quotes (”’) are used to write a multi-line comment, which helps in explaining in detail the use of the code. This helps to understand the code easily.
String formatting in Python helps to insert values inside a string in a structured way. Python provides different methods for formatting strings.
- format(): Place {} as placeholders and use .format() to insert values.
Syntax: “{}”.format(value)
- f-string: It is used to insert variables inside {} directly.
Syntax: f”text {variable}”
- % operator: It is used to insert values based on format specifiers.
Syntax: “%format_specifier” % value
Example:
Output:
Explanation: Here, each method inserts values into strings differently. The format() method uses {} as placeholders, f-string directly places variables inside {}, and the % operator follows the old formatting style.
Escape Sequences in Python
Escape sequences in Python refer to special characters that are employed to format the text output, such as introducing a new line or tab space.
Syntax Rules:
- \n: It adds a new line inside a string.
Syntax:
"text\ntext"
- \t: It inserts a tab space.
Syntax:
"text\ttext"
- \\: It prints a single backslash.
Syntax:
"C:\\path\\file"
- \’ and \”: It allows single or double quotes inside a string.
Syntax:
'It\'s a good day', "She said \"Hello\""
Example:
Output:
Explanation: Here, the escape sequences improve the structure of the output. \n adds a new line, \t creates spacing, \\ prints a backslash, and \” allows double quotes inside a string.
Operators and Expressions in Python
Python operators are used for performing different types of operations according to the input value or the variable. The Python expression is the combination of the values and operators for producing the result.
Syntax Rules:
- Arithmetic Operators: Used for mathematical calculations.
Syntax:
a + b, a - b, a * b, a / b, a % b, a // b, a ** b
- Comparison Operators: It is used for comparing the values and returning True or False.
Syntax:
a == b, a != b, a > b, a < b, a >= b, a <= b
- Logical Operators: ‘|’ help in combining multiple conditions.
Syntax:
a and b, a or b, not a
- Assignment Operators: It is used for assigning values and modifying variables.
Syntax:
a = b, a += b, a -= b, a *= b, a /= b, a //= b, a **= b
- Bitwise Operators: It is used for performing bit-level operations.
Syntax:
a & b, a | b, a ^ b, ~a, a << b, a >> b
Example:
Output:
Explanation: Here, different types of operators are used to perform various operations. Arithmetic operators perform mathematical calculations, comparison operators compare values, and logical operators combine the boolean values.
Functions in Python
Functions in Python are reusable blocks of code that are designed to perform a specific task. They help in improving the organization of the code, along with the readability and reusability.
1. Defining a Function in Python
The functions in Python are defined using the def keyword, which is then followed by a function name and optional parameters if required.
Syntax:
def function_name(parameters):
# function body
return value
2. Calling a Function in Python
A function is executed when it is called by its name, which is then followed by parentheses, passing arguments if there is any requirement.
Syntax:
function_name(arguments)
Example:
Output:
Explanation: Here, the greet function takes the name as an argument and returns a welcome message.
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Writing and Executing Your First Python Program
After mastering the Python syntax, it is time to write your first program. Start with a simple ‘Hello, World!’ program to understand how code is written and executed in Python.
There are two ways of writing and executing the program in Python the interactive and the scripting mode:
1. Executing in Interactive Mode
In the Python interactive mode, you can type and run the code directly in the terminal line by line. This is great when you want to test the code snippets and for quick outputs.
To start the Interactive Mode, open the terminal and type:
python3
Once Python starts, the prompt will change to:
>>
At the prompt, type the following command:
print("Hello, World!")
Output:
Explanation: Here, the print() will display text in the terminal window. The text is enclosed by double quotes and passed to print() as an argument. After pressing the Enter button, Python will execute the command immediately and display the output. After completing, exit the interactive window by passing the command exit().
2. Executing in the Script Mode
The script mode is useful for writing several lines of code that can be saved and run later. This is the most standard way for developers to write Python programs.
To create a new Python script file, open your terminal and type:
nano helloworld.py
(If you are using Windows, you can open any text editor, like Notepad, and save the file as helloworld.py.)
Now, inside the file, type the following code:
Save the file and close the editor.
Run Your Python Script
Once the script is ready, you have to run it by typing the following command in your terminal:
python3 helloworld.py
Output:
Explanation: Here, when the Python script is runs, the interpreter reads the code one line at a time and displays the output in the terminal. In this example, “Hello, World!” will be printed to the screen using the print() function.
This basic program confirms that you have installed Python and it is working correctly in your system. You can now experiment with variables, functions, control structures, and more by referring to the syntax that is explained above for all.
Conclusion
Python syntax does not utilize braces but rather uses indentation, which helps in increasing the readability of the code. Python does not use semicolons and is dynamically typed, so it is even easier for beginners to understand. With a clear and simple syntax, Python allows developers to focus more on logic rather than syntax errors. Mastering these syntax rules is essential for writing a clean, efficient, error-free program.
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Python Syntax – FAQs
Frequently Asked Questions
Q1. Why is indentation important in Python?
Indentation in Python is important because it determines the organization of the code. It indicates the statements that make up a loop, function, or condition, which helps the interpreter interpret the code correctly.
Q2. How do you write a comment in Python?
A single-line comment in Python is initiated by using the hashtag symbol #, and multi-line comments may be initiated and ended with three quotation marks (“””) or three single quotation marks (”’).
Q3. What are Python identifiers?
Identifiers in Python refer to the names of your variables, functions, or classes. An identifier must start with a letter or underscore.
Q4. How to print an output in Python?
Use the print() command to output the result to the console, for example – print(“I hope you understood Python syntax.
Q5. What are keywords in Python?
Keywords in Python are reserved words with special meaning, such as if, for, while, and class, and cannot be used as variable names.