colours = (('Yasoob', 'Yellow'),('Ali', 'Blue'),('Arham', 'Green'),
)
dict = {}
for name, colour in colours:dict[name] = colour
print(dict)
#output: {'Yasoob': 'Yellow', 'Ali': 'Blue', 'Arham': 'Green'}

print(dict['bob'])
#output:KeyError: 'bob'

dict1 = defaultdict(int)
dict2 = defaultdict(set)
dict3 = defaultdict(str)
dict4 = defaultdict(list)print(dict1[1])
print(dict2[1])
print(dict3[1])
print(dict4[1])output:
0      int的默认值
set()  set的默认值str的默认值
[]     list的默认值

s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
d = defaultdict(list)
for k, v in s:d[k].append(v)
print(d)output:
defaultdict(<class 'list'>, {'yellow': [1, 3], 'blue': [2, 4], 'red': [1]})

str = 'chinese'
d = defaultdict(int)
for k in str:d[k] += 1
print(d)output:
defaultdict(<class 'int'>, {'c': 1, 'h': 1, 'i': 1, 'n': 1, 'e': 2, 's': 1})

s = [('red', 1), ('blue', 2), ('red', 3), ('blue', 4), ('red', 1), ('blue', 4)]
d = defaultdict(set)
for k, v in s:d[k].add(v)
print(d)output:
defaultdict(<class 'set'>, {'red': {1, 3}, 'blue': {2, 4}})

strings = 'chinese'
counts = defaultdict(lambda: 0)
for i in strings:counts[i] +=1
print(counts)output:
defaultdict(<function <lambda> at 0x7fe1b1b3d170>, {'c': 1, 'h': 1, 'i': 1, 'n': 1, 'e': 2, 's': 1})#和int一样的效果

test = defaultdict(lambda : 'hello')
test[1]
test[2] = 'two'
print(test)output:
defaultdict(<function <lambda> at 0x7fe338b11170>, {1: 'hello', 2: 'two'})

s = [('red', 1), ('blue', 2), ('red', 3), ('blue', 4), ('red', 1), ('blue', 4)]
d = defaultdict(set)
for k, v in s:d[k].add(v)
print(d)
print(d.items())output:
defaultdict(<class 'set'>, {'red': {1, 3}, 'blue': {2, 4}})
dict_items([('red', {1, 3}), ('blue', {2, 4})])