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  Improving the performance of AWS Glue jobs involves several strategies that target different aspects of the ETL (Extract, Transform, Load) process. Here are some key practices. 1. Optimize Job Scripts Partitioning : Ensure your data is properly partitioned. Partitioning divides your data into manageable chunks, allowing parallel processing and reducing the amount of data scanned. Filtering : Apply pushdown predicates to filter data early in the ETL process, reducing the amount of data processed downstream. Compression : Use compressed file formats (e.g., Parquet, ORC) for your data sources and sinks. These formats not only reduce storage costs but also improve I/O performance. Optimize Transformations : Minimize the number of transformations and actions in your script. Combine transformations where possible and use DataFrame APIs which are optimized for performance. 2. Use Appropriate Data Formats Parquet and ORC : These columnar formats are efficient for storage and querying, signif

The Quick and Easy Way to Fix Python UnboundLocalError

Here is the easy way to fix the issue of the Python UnboundLocalError, allowing users to resolve any problems quickly.


UnboundLocalError



Python UnboundLocalError

While the variable in the function has already been defined, during execution, the result prints with an error of UnboundLocalError. Below, you will find an example that explains the issue and resolution.

Error: file 'example.txt' not found
Traceback (most recent call last):
File "main.py", line 16, in <module>
open_file("example.txt")
File "main.py", line 11, in open_file
if f:
UnboundLocalError: local variable 'f' referenced before assignment


** Process exited - Return Code: 1 **

Press Enter to exit terminal


Python program using try, except and finally

Below program explains how to use try, except and finally blocks in python. But during the execution, it prints UnboundLocalError.


Program using try, except and finally

# Define a function that may raise an exception
def open_file(filename):
    try:
        f = open(filename, "r")
        contents = f.read()
    except FileNotFoundError:
        print(f"Error: file '{filename}' not found")
    else:
        print(f"Contents of file '{filename}':\n{contents}")
    finally:
        if f:
            f.close()
            print(f"File '{filename}' has been closed.")

# Call the function with a valid filename
open_file("example.txt")

# Call the function with an invalid filename
open_file("invalid.txt")


The output:

Error: file 'example.txt' not found
Traceback (most recent call last):
  File "main.py", line 16, in <module>
    open_file("example.txt")
  File "main.py", line 11, in open_file
    if f:
UnboundLocalError: local variable 'f' referenced before assignment


** Process exited - Return Code: 1 **
Press Enter to exit terminal

Resolution for UnboundLocalError

In the function, before the try block, add f = None. That resolves the issue. Here is the corrected program.

Corrected program

# Define a function that may raise an exception
def open_file(filename):
    try:
        f = None
        f = open(filename, "r")
            contents = f.read()
    except FileNotFoundError:
        print(f"Error: file '{filename}' not found")
    else:
        print(f"Contents of file '{filename}':\n{contents}")
    finally:
        if f:
            f.close()
            print(f"File '{filename}' has been closed.")

# Call the function with a valid filename
open_file("example.txt")

# Call the function with an invalid filename
open_file("invalid.txt")


The output is:

Error: file 'example.txt' not found
Error: file 'invalid.txt' not found


** Process exited - Return Code: 0 **
Press Enter to exit terminal


Summary

  • Return statement not coded in the function. As a result, it gave UnboundLocalError.
  • A function returns the None object by default if the control flow falls off the end of the function body without running into a return statement.

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