A Rose by Any Other Name Invokes Just the Same

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A Rose by Any Other Name Invokes Just the Same
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Whats up Doc?

• This lecture is about functions
• Lambda
• Functions as variables
• Other cool and interesting stuff

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Functions are a special type of Variable

• def a(x)
• return x 1
• b a
• print b(x)
• What did we get?

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How do you invoke a function?

• () operator
• a
• The function
• a(5)
• The result of calling a with the parameter 5

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Why Does This Work?

• MyDictionary "a" lambda x x1, "b" lambda
  x x-1
• MyDictionary"a"(MyDictionary"b"(3))
• 3

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lambda

• Lamba is an expression that return a function
  that returns a result
• lamba parameters expression
• lamba x x 1
• b lamba x, y xy

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Map()

• Creates a new list after from the result of apply
  a function to each element of the list
• y 1,2,3
• x map(lambda z z1, y)
• x 2,3,4
• Can be use to merge multiple lists
• z map(lambda a,b min(a,b), x,y)
• y z

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Zip()

• Zip merges lists in a single list of tuples
• D 1,2,3,4,5
• E 10,11,12
• zip(D,E) (1,10),(2,11),(3,12)
• Zip return a list of len of the shortest list
  passed to it.

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Reduce()

• Takes a binary function and uses it to reduce a
  list to a single value
• a 1,2, 3, 4
• reduce(lambda r,l rl, a)
• Sums the list

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Filter

• Return a new sequence that has been filtered by a
  conditional
• filter(lambda x x 2 0, 1,2,3,4)

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List Comprehension

• expression for arg1 in sequence1 for argn in
  sequencen if condition
• 2 s for s in range(10)
• 2 s for s in range(10) if s 2 0