For 2023 (and 2024 ...) - we are now fully retired from IT training. We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.
Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!
I am also active in many other area and still look after a lot of web sites - you can find an index ((here)) |
UnboundLocalError - Python Message
What does THIS mean?
UnboundLocalError: local variable 'taxrate' referenced before assignment
It means that you have tried to modify the value of a variable - perhaps in a function - before you have given it an initial value:
taxrate = 15
def getnet(gross):
taxrate /= 100.
net = gross - gross / (1.0 + taxrate)
return net
amount = getnet (230)
print amount
The variable taxrate is local to the getnet function ... the way the code is written, there is a DIFFERENT taxrate variable in the calling code.
You could share the variable by declaring it global in the function or - much better - you could use it read only in the function, in which case Python will see it from the outer scope.
So this will work:
taxrate = 15
def getnet(gross):
net = gross - gross / (1.0 + taxrate/100.0)
return net
amount = getnet (230)
print amount
And that's also far better because it doesn't alter the variable that contains the tax rate - rather it leaves it available for later use. (written 2009-01-31)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles Y109 - Python - Exceptions [381] Exceptions in Python - (2005-07-17) [1042] Nested exceptions in Python - (2007-01-18) [1236] Trying things in Python - (2007-06-18) [2281] Python - using exceptions to set a fallback - (2009-07-12) [2368] Python - fresh examples of all the fundamentals - (2009-08-20) [2408] Robust user input (exception handling) example in Python - (2009-09-17) [2622] Handling unusual and error conditions - exceptions - (2010-02-03) [2994] Python - some common questions answered in code examples - (2010-10-10) [2998] Using an exception to initialise a static variable in a Python function / method - (2010-10-13) [3177] Insurance against any errors - Volcanoes and Python - (2011-02-19) [3433] Exceptions - a fail-safe way of trapping things that may go wrong - (2011-09-11) [3441] Pressing ^C in a Python program. Also Progress Bar. - (2011-09-15) [3664] Error checking in a Python program - making your program robust via exceptions - (2012-03-22) [3913] How many times ... has this loco headed west through Tenby? - Python exceptions - (2012-11-05) [3930] Reporting the full stack trace when you catch a Python exception - (2012-11-22) [4029] Exception, Lambda, Generator, Slice, Dict - examples in one Python program - (2013-03-04) [4161] Python varables - checking existance, and call by name or by value? - (2013-08-27) [4444] Elements of an exception in Python - try, except, else, finally - (2015-02-28)
Some other Articles
Pre and post increment - the ++ operatorShort health and safety courseLearning Python - many new example programsBaby Caleb and Fortune City in your web logs?UnboundLocalError - Python MessagePython - a truly dynamic languageApache httpd and Apache Tomcat miscellanyService Excellence AwardsFirst ClasswxPython - Introduction and sample
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This is a page archived from The Horse's Mouth at
http://www.wellho.net/horse/ -
the diary and writings of Graham Ellis.
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