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+--- Thread: Issue with a function (/thread-15125.html)
Issue with a function - ebolisa - Jan-05-2019
Hi,
No matter what number I select from the below code, the test() function is always fired. Why or, how to fix it?
TIA
#!/usr/bin/python3
import sys
# to test it:
# python3 testsys.py 1
# if we want to get 1
def f(x):
return {
'1':17,
'2':18,
'3':test(),
'4':23,
}[x]
def test():
print('testing funtion')
if __name__ == "__main__":
try:
a = f(sys.argv[1])
print('You selected {}'.format(a))
except RuntimeError:
print('Runtime Error')
except KeyError:
print('Wrong number')
RE: Issue with a function - buran - Jan-05-2019
on line 13, remove the
()def f(x):
return {
'1':17,
'2':18,
'3':test,
'4':23,
}[x]however, note that in case x==3 it will return a function object and not execute it.You need to elaborate further what you want to achieve.
To explain the problem in greater detail - when executing the f function it has to create the dict before being able to get value for key x from it. Because of the parenthesis it actually execute the test function, while creating the dict. If x==3 you will notice that it returns None.
On second thought, if you want to get the result of the test function
import sys
# to test it:
# python3 testsys.py 1
# if we want to get 1
def f(x):
return {
'1':17,
'2':18,
'3':test(),
'4':23,
}[x]
def test():
return 'testing funtion'
if __name__ == "__main__":
try:
a = f(sys.argv[1])
print('You selected {}'.format(a))
except RuntimeError:
print('Runtime Error')
except KeyError:
print('Wrong number')Note that it will always execute the test function, assign the return value to key 3 and only if x==3 it will get that value.