Difference between revisions of "CSC111 Exercises with Global Variables"

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(Created page with "--~~~~ ---- =Exercises= <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> [[category...")
 
 
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--[[User:Thiebaut|D. Thiebaut]] ([[User talk:Thiebaut|talk]]) 15:57, 24 April 2014 (EDT)
 
--[[User:Thiebaut|D. Thiebaut]] ([[User talk:Thiebaut|talk]]) 15:57, 24 April 2014 (EDT)
 
----
 
----
−
=Exercises=
+
<br />
 +
Explain the behavior of the different code sections shown below along with their output.
 +
<br />
 +
=Case 1=
 +
<br />
 +
{| class="wikitable" style="width:100%;"
 +
| style="width: 50%;" |
 +
<br />
 +
<source lang="python">
 +
A = 3
 +
 
 +
def f1( x ):
 +
    print( "f1", x, A )
 +
 
 +
print( "A = ", A )
 +
f1( 30 )
 +
 
 +
</source>
 +
<br />
 +
|
 +
<source lang="text">
 +
>>>
 +
A =  3
 +
f1 30 3
 +
>>>
 +
</source>
 +
|}
 +
 
 +
<br />
 +
 
 +
 
 +
<!-- ---------------------------------------------------------------------------------------------- -->
 +
<br />
 +
=Case  2=
 +
<br />
 +
{| class="wikitable" style="width:100%;"
 +
| style="width: 50%;" |
 +
<br />
 +
<source lang="python">
 +
def f1( x ):
 +
    print( "f1", x, A )
 +
 
 +
A = 3
 +
print( "A = ", A )
 +
f1( 30 )
 +
</source>
 +
<br />
 +
|
 +
<source lang="text">
 +
>>>
 +
A =  3
 +
f1 30 3
 +
>>>
 +
</source>
 +
|}
 +
 
 +
<!-- ---------------------------------------------------------------------------------------------- -->
 +
<br />
 +
=Case 3 =
 +
<br />
 +
{| class="wikitable" style="width:100%;"
 +
| style="width: 50%;" |
 +
<br />
 +
<source lang="python">
 +
A = 3
 +
 
 +
def f1( x ):
 +
    print( "f1", x, A )
 +
    A = 5
 +
   
 +
print( "A = ", A )
 +
f1( 30 )
 +
print( "A = ", A )
 +
 
 +
</source>
 +
<br />
 +
|
 +
>>>
 +
<font color="bue">A =  3</font>
 +
<font color="red">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</font>
 +
 +
>>>
 +
 
 +
|}
 +
 
 +
<!-- ---------------------------------------------------------------------------------------------- -->
 +
<br />
 +
 
 +
=Case 4 =
 +
<br />
 +
{| class="wikitable" style="width:100%;"
 +
| style="width: 50%;" |
 +
<br />
 +
<source lang="python">
 +
A = 3
 +
 
 +
def f1( x ):
 +
    global A
 +
    print( "f1", x, A )
 +
    A = 5
 +
   
 +
print( "A = ", A )
 +
f1( 30 )
 +
print( "A = ", A )
 +
 
 +
 
 +
</source>
 +
<br />
 +
|
 +
<source lang="text">
 +
>>>
 +
A =  3
 +
f1 30 3
 +
A =  5
 +
>>>
 +
</source>
 +
|}
 +
 
 +
<!-- ---------------------------------------------------------------------------------------------- -->
 +
<br />
 +
 
 +
=Case  5=
 +
<br />
 +
{| class="wikitable" style="width:100%;"
 +
| style="width: 50%;" |
 +
<br />
 +
<source lang="python">
 +
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 )
 +
 
 +
 
 +
</source>
 +
<br />
 +
|
 +
<source lang="text">
 +
>>>
 +
A =  [1, 2, 3]
 +
f1 30 []
 +
f1 30 [10, 20]
 +
A =  [1, 2, 3]
 +
>>>
 +
</source>
 +
|}
 +
 
 +
<!-- ---------------------------------------------------------------------------------------------- -->
 +
<br />
 +
 
 +
=Case  6=
 +
<br />
 +
{| class="wikitable" style="width:100%;"
 +
| style="width: 50%;" |
 +
<br />
 +
<source lang="python">
 +
 
 +
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 )
 +
 
  
 +
</source>
 
<br />
 
<br />
 +
|
 +
<source lang="text">
 +
>>>
 +
A =  [1, 2, 3]
 +
f1 30 []
 +
f1 30 [10, 20]
 +
A =  [10, 20]
 +
>>>
 +
</source>
 +
|}
 +
 +
<!-- ---------------------------------------------------------------------------------------------- -->
 
<br />
 
<br />
 +
 +
=Case  7=
 
<br />
 
<br />
 +
{| class="wikitable" style="width:100%;"
 +
| style="width: 50%;" |
 +
<br />
 +
<source lang="python">
 +
 +
def f1( x ):
 +
    A = x
 +
 +
def f2( ):
 +
    print( "f2", A )
 +
   
 +
f1( 10 )
 +
f2()
 +
 +
</source>
 +
<br />
 +
|
 +
>>>
 +
<font color="red">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</font>
 +
>>>
 +
|}
 +
 +
 +
<br />
 +
=Case  8=
 +
<br />
 +
{| class="wikitable" style="width:100%;"
 +
| style="width: 50%;" |
 +
<br />
 +
<source lang="python">
 +
def f1( x ):
 +
    global A
 +
    A = x
 +
 +
def f2( ):
 +
    global A
 +
    print( "f2", A )
 +
   
 +
f1( 10 )
 +
f2()
 +
 +
</source>
 +
<br />
 +
|
 +
<source lang="text">
 +
>>>
 +
f2 10
 +
>>>
 +
</source>
 +
|}
 +
 +
 
<br />
 
<br />
 
<br />
 
<br />

Latest revision as of 19:34, 24 April 2014

--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
 >>>



















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