How to handle exception inside a Python for loop?

You can handle exceptions inside a Python for loop using try-except blocks. There are two main approaches: handling exceptions for each iteration individually, or handling exceptions for the entire loop.

Exception Handling Per Iteration

Place the try-except block inside the loop to handle exceptions for each iteration separately ?

for i in range(5):
    try:
        if i % 2 == 0:
            raise ValueError(f"Error at iteration {i}")
        print(f"Processing: {i}")
    except ValueError as e:
        print(f"Caught exception: {e}")

Caught exception: Error at iteration 0
Processing: 1
Caught exception: Error at iteration 2
Processing: 3
Caught exception: Error at iteration 4

Exception Handling for Entire Loop

Place the try-except block around the entire loop to catch any exception that breaks the loop ?

try:
    for i in range(5):
        if i == 3:
            raise ValueError("Critical error - stopping loop")
        print(f"Processing: {i}")
except ValueError as e:
    print(f"Loop interrupted: {e}")

Processing: 0
Processing: 1
Processing: 2
Loop interrupted: Critical error - stopping loop

Practical Example with File Processing

Here's a real-world example processing a list of files where some might not exist ?

files = ['data1.txt', 'data2.txt', 'missing.txt', 'data3.txt']

for filename in files:
    try:
        # Simulate file reading
        if filename == 'missing.txt':
            raise FileNotFoundError(f"File {filename} not found")
        print(f"Successfully processed: {filename}")
    except FileNotFoundError as e:
        print(f"Skipping file: {e}")
    except Exception as e:
        print(f"Unexpected error with {filename}: {e}")

Successfully processed: data1.txt
Successfully processed: data2.txt
Skipping file: File missing.txt not found
Successfully processed: data3.txt

Comparison

Conclusion

Use try-except inside the loop to handle individual iteration errors and continue processing. Use try-except outside the loop when any error should stop the entire operation.