ARGUMENT NUANCES

• In Python function invocations, copies of the values of arguments are used to initialize the parameters. This style of parameter passing is known as pass by value.

• Because copies are used, the values of the arguments cannot be modified within the function being invoked.

SETUP

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

f()

rmbr

x

y

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

f()

rmbr

x

y

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

f()

rmbr

x

y

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

f()

rmbr

x

y

f()

rmbr

x

y

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

f()

rmbr

x

y

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

f()

rmbr

x

y

Program cautionary.py

import tale

city1 = 'London'

city2 = 'Paris’

tale.f( city1, city2 )

print( city1, city2 )

PYTHON FILES

Module tale.py

def f( x, y ) :

rmbr = x

x = y

y = rmbr

main

city1

city2

’London'

'Paris'

f()

rmbr

x

y

main

city1

city2

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def zero( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 3 1 4

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 3 1 4

out()

x

i

n

out()

x

i

n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 3 1 4

out()

x

i

n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 3 1 4

out()

x

i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 3 1 4

out()

x

i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 3 1 4

out()

x

0 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 3 1 4

out()

x

0 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 3 1 4

out()

x

0 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 1 4

out()

x

0 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 1 4

out()

x

1 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 1 4

out()

x

1 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 1 4

out()

x

1 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 0 4

out()

x

1 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 0 4

out()

x

2 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 0 4

out()

x

2 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 0 4

out()

x

2 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 0 0

out()

x

2 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 0 0

out()

x

2 i

3 n

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 0 0

main

nbrs

Program wipe.py

import zero

nbrs = [ 3, 1, 4 ]

zero.out( nbrs )

print( nbrs )

PYTHON FILES

Module zero.py

def out( x) :

n = len( x )

for i in range( 0, n ) :

x[ i ] = 0

main

nbrs 0 0 0

main

nbrs