python快速入门【二】----常见的数据结构

# Defining a dictionary
webstersDict = {'person': 'a human being, whether an adult or child', 'marathon': 'a running race that is about 26 miles', 'resist': ' to remain strong against the force or effect of (something)', 'run': 'to move with haste; act quickly'}

webstersDict

{'marathon': 'a running race that is about 26 miles',
 'person': 'a human being, whether an adult or child',
 'resist': ' to remain strong against the force or effect of (something)',
 'run': 'to move with haste; act quickly'}

# Finding out the meaning of the word marathon
# dictionary[key]
webstersDict['marathon']

'a running race that is about 26 miles'

# add one new key value pair to dictionary
webstersDict['shoe'] = 'an external covering for the human foot'

# return the value for the 'shoe' key
webstersDict['shoe']

'an external covering for the human foot'

# update method, update or add more than key value pair at a time 
webstersDict.update({'shirt': 'a long- or short-sleeved garment for the upper part of the body'
                     , 'shoe': 'an external covering for the human foot, usually of leather and consisting of a more or less stiff or heavy sole and a lighter upper part ending a short distance above, at, or below the ankle.'})
webstersDict

{'marathon': 'a running race that is about 26 miles',
 'person': 'a human being, whether an adult or child',
 'resist': ' to remain strong against the force or effect of (something)',
 'run': 'to move with haste; act quickly',
 'shirt': 'a long- or short-sleeved garment for the upper part of the body',
 'shoe': 'an external covering for the human foot, usually of leather and consisting of a more or less stiff or heavy sole and a lighter upper part ending a short distance above, at, or below the ankle.'}

# Removing key from dictionary
del webstersDict['resist']
webstersDict

{'marathon': 'a running race that is about 26 miles',
 'person': 'a human being, whether an adult or child',
 'run': 'to move with haste; act quickly',
 'shirt': 'a long- or short-sleeved garment for the upper part of the body',
 'shoe': 'an external covering for the human foot, usually of leather and consisting of a more or less stiff or heavy sole and a lighter upper part ending a short distance above, at, or below the ankle.'}

webstersDict[['sock']] = 'a short stocking usually reaching to the calf or just above the ankle.'

# incorporate into get example and such below. 
storyCount = {'is': 100, 'the': 90, 'Michael': 12, 'runs': 5}

storyCount

{'Michael': 12, 'is': 100, 'runs': 5, 'the': 90}

# key error for keys that do not exist
storyCount['run']

# if key doesnt exist, 
# specify default value for keys that dont exist. 
# returns value for key you enter if it is in dictionary
# else it returns the value you have for default
storyCount.get('Michael', 0)

12

# When you dont set default value for key that doesnt exist, 
# it defaults to none
print(storyCount.get('run'))

None

# Making default value for key that doesn't exist 0. 
print(storyCount.get('run', 0))

0

count = storyCount.pop('the')
print(count)

90

# return keys in dictionary
print(storyCount.keys())

# return values in dictionary
print(storyCount.values())

['is', 'runs', 'Michael']
[100, 5, 12]

# iterate through keys
for key in storyCount: 
    print(key)

is
runs
Michael

# iterate through keys and values
for key, value in webstersDict.items():
    print(key, value)

('person', 'a human being, whether an adult or child')
('run', 'to move with haste; act quickly')
('shoe', 'an external covering for the human foot, usually of leather and consisting of a more or less stiff or heavy sole and a lighter upper part ending a short distance above, at, or below the ankle.')
('marathon', 'a running race that is about 26 miles')
('shirt', 'a long- or short-sleeved garment for the upper part of the body')

# Way 1
emptyTuple = ()

# Way 2
emptyTuple = tuple()

# way 1
z = (3, 7, 4, 2)

# way 2 (tuples can also can be created without parenthesis)
z = 3, 7, 4, 2

# tuple with one value
tup1 = ('Michael',)

# tuple with one value
tup2 = 'Michael', 

# This is a string, NOT a tuple.
notTuple = ('Michael')

# Initialize a tuple
z = (3, 7, 4, 2)

# Access the first item of a tuple at index 0
print(z[0])

3

# print last item in the tuple
print(z[-1])

2

print(z[3])

2

# Initialize a tuple
z = (3, 7, 4, 2)

# first index is inclusive (before the :) and last (after the :) is not.
print(z[0:2])

(3, 7)

# everything up to but not including index 3
print(z[:3])

(3, 7, 4)

print(z[-4:-1])

(3, 7, 4)

z = (3, 7, 4, 2)

z[1] = "fish"

# Initialize tuple
tup1 = ('Python', 'SQL')

# Initialize another Tuple
tup2 = ('R',)

# Create new tuple based on existing tuples
new_tuple = tup1 + tup2;
print(new_tuple)

('Python', 'SQL', 'R')

# Initialize a tuple
animals = ('lama', 'sheep', 'lama', 48)

print(animals.index('lama'))

0

print(animals.count('lama'))

2

for item in ('lama', 'sheep', 'lama', 48):
    print(item)

lama
sheep
lama
48

x, y = (7, 10);
print("Value of x is {}, the value of y is {}.".format(x, y))

Value of x is 7, the value of y is 10.

friends = ('Steve', 'Rachel', 'Michael', 'Monica')
for index, friend in enumerate(friends):
    print(index,friend)

(0, 'Steve')
(1, 'Rachel')
(2, 'Michael')
(3, 'Monica')

import timeit 
print('Tuple time: ', timeit.timeit('x=(1,2,3,4,5,6,7,8,9,10,11,12)', number=1000000))
print('List time: ', timeit.timeit('x=[1,2,3,4,5,6,7,8,9,10,11,12]', number=1000000))

('Tuple time: ', 0.0192110538482666)
('List time: ', 0.16498994827270508)

bigramsTupleDict = {('this', 'is'): 23,
                    ('is', 'a'): 12,
                    ('a', 'sentence'): 2}

print(bigramsTupleDict)

{('is', 'a'): 12, ('this', 'is'): 23, ('a', 'sentence'): 2}

bigramsListDict = {['this', 'is']: 23,
                   ['is', 'a']: 12,
                   ['a', 'sentence']: 2}

print(bigramsListDict)

graphicDesigner = {('this', 'is'),
                   ('is', 'a'),
                   ('a', 'sentence')}
print(graphicDesigner)

set([('is', 'a'), ('this', 'is'), ('a', 'sentence')])

graphicDesigner = {['this', 'is'],
                   ['is', 'a'],
                   ['a', 'sentence']}
print(graphicDesigner)

print(1, 1, 2, 3, 5, 8, 13, 21, 34, 55)

1 1 2 3 5 8 13 21 34 55

# Note, there are better ways to code this which I will go over in later videos
a,b = 1,1
for i in range(10):
    print("Fib(a): ", a, "b is: ", b)
    a,b = b,a+b   

('Fib(a): ', 1, 'b is: ', 1)
('Fib(a): ', 1, 'b is: ', 2)
('Fib(a): ', 2, 'b is: ', 3)
('Fib(a): ', 3, 'b is: ', 5)
('Fib(a): ', 5, 'b is: ', 8)
('Fib(a): ', 8, 'b is: ', 13)
('Fib(a): ', 13, 'b is: ', 21)
('Fib(a): ', 21, 'b is: ', 34)
('Fib(a): ', 34, 'b is: ', 55)
('Fib(a): ', 55, 'b is: ', 89)