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Table of contents
1.
Introduction
2.
What is Invalid Syntax in Python?
2.1.
Example:
3.
Catching SyntaxError Exceptions in Python
4.
Fixing Invalid SyntaxError in Python
4.1.
Python
5.
Reasons for Syntax Errors in Python 
5.1.
Missing of brackets
5.2.
Inconsistent indentation
5.3.
Python
5.4.
Missing of Colon
5.5.
Python
5.6.
Using keywords as a variable name
5.7.
Python
5.8.
Not Understanding the difference between “=” and “==”
5.9.
Python
5.10.
Non-Matching Quotation marks
5.11.
Python
6.
Frequently Asked Questions
6.1.
What do you mean by Syntax in Python?
6.2.
How can one fix the invalid syntax in Python?
6.3.
What are the different types of programming errors?
6.4.
Why am I getting invalid syntax in Python for no reason?
7.
Conclusion
Last Updated: Mar 27, 2024
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Invalid Syntax in Python: Common Reasons for SyntaxError

Author Urwashi Priya
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Basics of Python
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Introduction

Let’s start discussing the invalid syntax in Python, which leads to Syntax errors. First of all, let us have a brief introduction to Python and the reasons behind this error. 

invalid syntax

Python is written in a very layman language. A newbie coder could learn Python easily compared to any other language. So, what happens is if a person switches from another language, syntax changes which leads to confusion and results in the formation of error.

So, here we will be discussing all possible errors made. We will also discuss how to avoid them. Let’s start understanding what is invalid Syntax in Python or common reasons for syntax errors in Python.

You can also read about the Multilevel Inheritance in Python, Swapcase in Python

What is Invalid Syntax in Python?

While running our code, when the output doesn’t display on our screen, most certainly, it’s a syntax error. 

invalid image

In other words, when the python interpreter fails to give the output on the screen, this arises the case of invalid syntax. The interpreter also shows the line number where the error has occurred. This helps in traceback and correcting errors.

Example:

This is an example of a Python code throwing a SyntaxError:

print("Hello, world!"

 

As we can see the brackets is not closed so this will throw an SyntaxError.

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Catching SyntaxError Exceptions in Python

Syntax errors in Python can be caught using try-except blocks. However, SyntaxError exceptions are typically not caught at runtime because they indicate invalid Python code that needs to be fixed during development.

Example:

try:
   exec("print('Hello, world!'")
except SyntaxError as e:
   print("Syntax error occurred:", e)

Fixing Invalid SyntaxError in Python

To fix SyntaxError in Python, carefully review the code for any missing parentheses, brackets, colons, or other syntax errors, and correct them accordingly.

Example:

  • Python

Python

print("Hello, world!")

Output

Hello, world!

Reasons for Syntax Errors in Python 

Syntax errors in Python occur due to incorrect use of Python syntax rules, such as missing or mismatched brackets, parentheses, colons, or quotes, or incorrect indentation levels.

Now we will be discussing common reasons for syntax errors in python.

Missing of brackets

print("Hello world."

 

Output

ERROR!
Traceback (most recent call last):
 File "<main.py>", line 1
   print("Hello world."
        ^
SyntaxError: '(' was never closed

Here we can see that the output screen clearly shows that a bracket is missing at the end.

Inconsistent indentation

  • Python

Python

def one():
   return 1

def two():
   return 2
   
print("Choose operation.")
print("1.Return 1")
print("2.Return 2")

while True:
   choice = input("Enter 1 or 2: ")
   if choice in ('1', '2'):
#incorrect indentation
   if choice == '1':
           print("1")

       elif choice == '2':
           print("2")
      
       next = input("Print again? (yes/no): ")
       if next == "no":
         break
  
   else:
       print("Invalid Input")

Output

ERROR!
Traceback (most recent call last):
 File "<main.py>", line 15
   if choice == '1':
   ^^
IndentationError: expected an indented block after 'if' statement on line 13

 

Indentation plays an important role in python code. Wrong indentation results in an error in Python. Here, the output screen indicates where indentation is wrongly used.

Missing of Colon

  • Python

Python

#Missing of colon
def one()
   return 1

def two():
   return 2

print("Choose operation.")
print("1.Return 1")
print("2.Return 2")

while True:
   choice = input("Enter 1 or 2: ")
   if choice in ('1', '2'):
   if choice == '1':
           print("1")

       elif choice == '2':
           print("2")
      
       next = input("Print again? (yes/no): ")
       if next == "no":
         break
  
   else:
       print("Invalid Input")

Output

ERROR!
Traceback (most recent call last):
 File "<main.py>", line 2
   def one()
            ^
SyntaxError: expected ':'

 

After any function or compound statement such as if, else, while, for, the colon is required after the condition.

Also see,  Convert String to List Python

Using keywords as a variable name

  • Python

Python

def one():
   return 1

def two():
   return 2

print("Choose operation.")
print("1.Return 1")
print("2.Return 2")

while True:
   #keyword used as a variable name
   def = input("Enter 1 or 2: ")
   if def in ('1', '2'):
       if def == '1':
           print("1")

       elif def == '2':
           print("2")
      
       next = input("Print again? (yes/no): ")
       if next == "no":
         break
  
   else:
       print("Invalid Input")

Output

ERROR!
Traceback (most recent call last):
 File "<main.py>", line 13
   def = input("Enter 1 or 2: ")
       ^
SyntaxError: invalid syntax

 

def is a keyword in Python. So, using it results in invalid syntax.

Not Understanding the difference between “=” and “==”

  • Python

Python

def one():
   return 1

def two():
   return 2

print("Choose operation.")
print("1.Return 1")
print("2.Return 2")

while True:
   #using == instead of =
   def == input("Enter 1 or 2: ")
   if def in ('1', '2'):
       if def == '1':
           print("1")

       elif def == '2':
           print("2")
      
       next = input("Print again? (yes/no): ")
       if next == "no":
         break
  
   else:
       print("Invalid Input")
       

Output

ERROR!
Traceback (most recent call last):
 File "<main.py>", line 13
   def == input("Enter 1 or 2: ")
       ^^
SyntaxError: invalid syntax

 

“=” is used for assigning something, and “==” is used for checking the equality condition.

Non-Matching Quotation marks

  • Python

Python

print("Hello World')

Output

ERROR!
Traceback (most recent call last):
 File "<main.py>", line 1
   print("Hello World')
         ^
SyntaxError: unterminated string literal (detected at line 1)

 

If the string contained in quotation marks starts with double quotes, it should end with double quotes.

In Python code, indentation plays the most important part. Make sure that your code is well indented. You can try it on online python compiler.


It's time to discuss some FAQs related to the Invalid Syntax in Python.

Frequently Asked Questions

What do you mean by Syntax in Python?

Syntax generally refers to a set of rules predefined to be followed to come up with the correct output.

How can one fix the invalid syntax in Python?

Read the error message properly. Tracebacks are good enough to find the reason for mistakes in your code.

What are the different types of programming errors?

Basically, there are three different types of programming errors: Syntax error, Runtime error and logical errors.

Why am I getting invalid syntax in Python for no reason?

Invalid syntax errors in Python typically occur due to missing or mismatched brackets, parentheses, colons, or quotes, or incorrect indentation levels in the code.

Conclusion

We have discussed the Invalid Syntax in Python, including its example and the error that would be displayed on the output screen. 

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