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Undefined values: Difference between revisions
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echo "Done\n";
?></lang>
Results in:
<pre>var is undefined at first check
var is undefined at third check
Done
</pre>
=={{header|Python}}==
<lang python>
# Check to see whether it is defined
try: var
except NameError: print "var is undefined at first check"
# Give it a value
var = "Chocolate"
# Check to see whether it is defined after we gave it the
# value "Chocolate"
try: var
except NameError: print "var is undefined at second check"
# Give the variable an undefined value.
del var
# Check to see whether it is defined after we've explicitly
# given it an undefined value.
try: var
except NameError: print "var is undefined at third check"
# Give the variable a value of 42
var = 42
# Check to see whether the it is defined after we've given it
# the value 42.
try: var
except NameError: print "var is undefined at fourth check"
# Because most of the output is conditional, this serves as
# a clear indicator that the program has run to completion.
print "Done"
</lang>
Results in:
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