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cs_lec_16

Lists in Environment Diagram Assume that before each example below we execute s=[2,3] t=[5,6]

Operation: Append adds one element to the list Example: s.append(t) t=0 Result: s -> [2,3,[5,6]] t->0

Operation Extend combines list elements one after another a = [1,[2]] b=[[3],4] c = a+b d=[a,b]

Operation addition and slicing creates new lists containing existing elements a=s+[t] b=a[1:] a[1] = 9 b[1][1]=0

The list function also creates a new list contianing existing elements t=list(s) s[1] = 0

a = [1,[2],3] b = list(a) So in this case we would have bb is aa, ![[chrome_KJwaFV9XZz.png]] ![[chrome_jNdnZFw6Sg.png]] List in Lists in Lists in Environment Diagrams t=[1,2,3] t[1:3] = [t] t.extend(t) So the above example will return: t=[1, [...], 1, [...]], where the ...... basically represents tt nested within the original list t.

t = [[1,2],[3,4]] t[0].append(t[1:2])

![[WhatsApp Image 2022-10-21 at 1.43.02 PM.jpeg]] ![[WhatsApp Image 2022-10-21 at 1.45.55 PM.jpeg]] john.elf.work(john) -> 'Peon, I work'

Example: Iterables and Iterators Using BUilt-in Functions and Comprehensions What are the indices of all elements in a list s that have the smallest absolute value?

def min_abs_indices(s):
    min_abs = min(map(abs,s))
    return [i for i in range(len(s)) if s[i] == min_abs]

What's the largest sum of two adjacent elements in a list s? (Assume len(s) > 1)

def sum_indices(s):
    return max([s[i]+s[i+1] for i in range(len(s)-1)])

Another method

def sum_indices(s):
    return list(zip(s[0:len(s)-1],s[1:]))

Create a dictionary mapping each digit d to the lists of elements in s that end with d.

def dic_comprehension(s):
    lis = [n%10 for i in s]
    return {i: [x for x in s if x%10==i] for i in range(10) if i in [n%10 for n in s]}