1) Operation subroutine of global variables, such as
val=9
def test(flag):
if flag:
val = 1
else:
print 'Error'
return val
test(0)
Error: UnboundLocalError: local variable 'val' referenced before assignment Solution: global keyword to be indicating that the variable is a global variable
val=9
def test(flag):
global val
if flag:
val = 1
else:
print 'test'
return val
test(0)2) local variable, but still reported a problem unboundLocal Error
such as:
def test（flag）：
if （a）：
bbb = aaa
elif（b）：
bbb2 = aaa2
print(bbb2)Error: UnboundLocalError: local variable 'bbb2' referenced before assignment
reason given is that python think bbb2 not necessarily be assigned.
Solution: The first assignment for bbb2
def test（flag）：
bbb2=0
if （a）：
bbb = aaa
elif（b）：
bbb2 = aaa2
print(bbb2)