UnboundLocalError Local Variable 'index' Referenced Before Assignment
Evan Hicks
—The Problem
The exception UnboundLocalError: local variable 'index' referenced before assignment happens in Python when you use a global variable in a function that also defines a local version of the same variable.
index = 0 def foo(): if index == 0: print("ZERO") index = 1 foo()
Because index is defined globally as well as inside the foo() function, Python throws an exception if you try to use the variable inside foo before it’s declared.
The Solution
In this case, we want to rename the variable to avoid the conflict.
index = 0 def foo(): if index == 0: print("ZERO") findex = 1 foo()
Further Reading
If you’re looking to get a deeper understanding of how Python application monitoring works, take a look at the following articles:
- Sentry BlogPython Performance Testing: A Comprehensive Guide
- Syntax.fmListen to the Syntax Podcast
- Sentry BlogLogging in Python: A Developer’s Guide
- CodecovPython - Codecov
- Listen to the Syntax Podcast
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