Python Idioms

pythonTutorials.py

# zip([iterable, ...])
# This function returns a list of tuples, 
# where the i-th tuple contains the i-th 
# element from each of the argument sequ-
# ences or iterables.
a = [1, 2, 3, 4, 5, 6];
b = [6, 5, 4, 3, 2, 1];
c = [cA*cB for cA, cB in zip(a, b)]; # c = [6, 10, 12, 12, 10, 6]

# Sorting using keys
# More at https://wiki.python.org/moin/HowTo/Sorting
d = [-2, -23, 32, -3, 0, -34];
print sorted(d, key = lambda x:abs(x), reverse = True);
# OUTPUT = [-34, 32, -23, -3, -2, 0]

# map(function, iterable, ...)
# Apply function to every item of iterable
# and return a list of the results. 
print map(hash, b); # This will hash all the ints in b

# lambda - creating anonymous inline functions
print (lambda x, y: x*y)(3, 4); # OUTPUT = 4
incrementer = lambda input: input + 1;
# above is same as def incrementer(input): return input+1
# now we call it
print incrementer(3); # OUTPUT = 12

# lambda and map together
squares = map(lambda x: x**2, range(10));
print squares # OUTPUT = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

# filter 
# Filter takes a function returning True or False and applies
# it to a sequence, returning a list of only those members of 
# the sequence for which the function returned True.
special_squares = filter(lambda x: x > 5 and x < 50, squares);