List Statements

The Assignment Statement. The variation on the assignment statement called multiple-assignment statement also works with lists. We looked at this in the section called “Multiple Assignment Statement”. Multiple variables are set by decomposing the items in the list.

>>> 
x,y=[1,"hi"]

>>> 
x

1
>>> 
y

"hi"
            

This will only work of the list has a fixed and known number of elements. This is more typical when working with tuples, which are immutable, rather than lists, which can vary in length.

The for Statement. The for statement also works directly with sequences like list. The range function that we have used creates a list. We can also create lists other ways. We'll touch on various list construction techniques at several points in the text.

s= 0
for i in [2,3,5,7,11,13,17,19]:
    s += i
print "total",s

The del Statement. The del statement removes items from a list. For example

>>> 
i = range(10)

>>> 
del i[0],i[2],i[4],i[6]

>>> 
i

[1, 2, 4, 5, 7, 8]
            

This example reveals how the del statement works.

The i variable starts as the list [0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ].

Remove i[0] and the variable is [1, 2, 3, 4, 5, 6, 7, 8, 9].

Remove i[2] (the value 3) from this new list, and get [1, 2, 4, 5, 6, 7, 8, 9].

Remove i[4] (the value 6) from this new list and get [1, 2, 4, 5, 7, 8, 9].

Finally, remove i[6] and get [1, 2, 4, 5, 7, 8].