CSC111 Exercises with Global Variables
--D. Thiebaut (talk) 15:57, 24 April 2014 (EDT)
Explain the behavior of the different code sections shown below along with their output.
Case 1
|
A = 3
def f1( x ):
print( "f1", x, A )
print( "A = ", A )
f1( 30 )
|
>>>
A = 3
f1 30 3
>>>
|
Case 2
|
def f1( x ):
print( "f1", x, A )
A = 3
print( "A = ", A )
f1( 30 )
|
>>>
A = 3
f1 30 3
>>>
|
Case 3
|
A = 3
def f1( x ):
print( "f1", x, A )
A = 5
print( "A = ", A )
f1( 30 )
print( "A = ", A )
|
>>> A = 3 Traceback (most recent call last): File "/Users/thiebaut/Desktop/PYTHON/globalExercises.py", line 8, in <module> f1( 30 ) File "/Users/thiebaut/Desktop/PYTHON/globalExercises.py", line 4, in f1 print( "f1", x, A ) UnboundLocalError: local variable 'A' referenced before assignment >>> |
Case 4
|
A = 3
def f1( x ):
global A
print( "f1", x, A )
A = 5
print( "A = ", A )
f1( 30 )
print( "A = ", A )
|
>>>
A = 3
f1 30 3
A = 5
>>>
|
Case 5
|
def f1( x ):
A = []
print( "f1", x, A )
A.append( 10 )
A.append( 20 )
print( "f1", x, A )
A = [1, 2, 3]
print( "A = ", A )
f1( 30 )
print( "A = ", A )
|
>>>
A = [1, 2, 3]
f1 30 []
f1 30 [10, 20]
A = [1, 2, 3]
>>>
|
Case 6
|
def f1( x ):
global A
A = []
print( "f1", x, A )
A.append( 10 )
A.append( 20 )
print( "f1", x, A )
A = [1, 2, 3]
print( "A = ", A )
f1( 30 )
print( "A = ", A )
|
>>>
A = [1, 2, 3]
f1 30 []
f1 30 [10, 20]
A = [10, 20]
>>>
|
Case 7
|
def f1( x ):
A = x
def f2( ):
print( "f2", A )
f1( 10 )
f2()
|
>>> Traceback (most recent call last): File "/Users/thiebaut/Desktop/PYTHON/globalExercises.py", line 9, in <module> f2() File "/Users/thiebaut/Desktop/PYTHON/globalExercises.py", line 6, in f2 print( "f2", A ) NameError: global name 'A' is not defined >>> |
Case 8
|
def f1( x ):
global A
A = x
def f2( ):
global A
print( "f2", A )
f1( 10 )
f2()
|
>>>
f2 10
>>>
|
