Learning by doing: Reading books and trying to understand the (code) examples
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from collections import defaultdict
stocks = {"GOOG": (613.30, 625.86, 610.50),
"MSFT": (30.25, 30.70, 30.19)}
# different possibilities to get values from the dictionary
print("GOOG: {}".format(stocks["GOOG"]))
print("RIM: {}".format(stocks.get("RIM", "NOT FOUND")))
stocks.setdefault("RIM", (67.38, 68.48, 67.28))
print("RIM: {}".format(stocks["RIM"]))
for stock, values in stocks.items():
print("{} last value is {}".format(stock, values[0]))
random_keys = {}
random_keys["astring"] = "somestring"
random_keys[5] = "aninteger"
random_keys[25.2] = "floats work too"
random_keys[("abc", 123)] = "so do tuples"
class AnObject(object):
def __init__(self, avalue):
self.avalue = avalue
my_object = AnObject(14)
random_keys[my_object] = "We can even store objects"
my_object.avalue = 12
try:
random_keys[[1, 2, 3]] = "We can't store lists though"
except:
print("unable to store list \n")
for key, value in random_keys.items():
print("{} has value {}".format(key, value))
if hasattr(key, "avalue"):
print("{}.avalue ={}".format(key, key.avalue))
def letter_frequency(sentence):
frequencies = {}
for letter in sentence:
frequency = frequencies.setdefault(letter, 0)
frequencies[letter] = frequency + 1
return frequencies
print(letter_frequency("Hello world, what's going on?"))
# defaultdict using built-in function
def letter_frequency_defdict(sentence):
frequencies = defaultdict(int)
for letter in sentence:
frequencies[letter] += 1
return frequencies
print(letter_frequency_defdict("Hello world, what's going on?"))
# defaultdict using self defined function
num_items = 0
def tuple_counter():
global num_items
num_items += 1
return num_items, []
d = defaultdict(tuple_counter)
d['a'][1].append("hello")
d['b'][1].append("world")
print(d)