Python基础语法

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# Boolean and its Operations
print(type(True))
print(type(False))
print(type(None))

# 输出如下所示：
"""
<class 'bool'>
<class 'bool'>
<class 'NoneType'>
"""

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# and or
B = True
A = False

print(B and True)
print(A or B)
print(not B)
print(not A)
print(B and (not A))

# 输出如下所示：
"""
True
True
False
True
True
"""

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# Expressions can evaluate to a boolean value
print(3 >= 2)
print(2 >= 2)
print(A is A)
print(A is B)
print(3 != 2)

# 输出如下所示：
"""
True
True
True
False
True
"""

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# Integer and floats
print(type(3))
print(type(3.0))

# 输出如下所示：
"""
<class 'int'>
<class 'float'>
"""

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# Numerical operations
import math

print(3 / 2)
print(5 // 2)
print(3 % 2)
print(float(3))
print(pow(2, 3))
print(math.ceil(3.4))
print(math.floor(3.4))
print(round(3.1415926, 2))

# 输出如下所示：
"""
1.5
2
1
3.0
8
4
3
3.14
"""

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# String
Introduction = 'Today is 2019-01-21'
print(Introduction)
print(str(3))
print(int('3'))
print(str("b'AS"))

# String Method
A = 'abc'
print(A.capitalize())
print(A.upper())
print(A.find('b'))
print(A.find('d'))

# String formatting
s = 'My name is Tom'
name = 'Tomas'
age = 25
score = 98.532421
print('hello, my name is %s and I am %d years old\n \ I scored %f on my midterm'%(name, age, score))
print('hello, my name is %s and I am %d years old\n \
I scored %.2f on my midterm'%(name, age, score))

# 输出如下所示：
"""
Today is 2019-01-21
3
3
b'AS

Abc
ABC
1
-1

hello, my name is Tomas and I am 25 years old
 \ I scored 98.532421 on my midterm
hello, my name is Tomas and I am 25 years old
 I scored 98.53 on my midterm
"""

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# List 
# Create and Modify list
A = []
A.append(1)
A
# List index and Slicing
# length = n, start from 0 and end at (n-1)
A = [1, 2, 3, 4, 5, 6]
print(len(A))
print(A[0])
A[0] = 100
print(A[0])
A[1:4]
print(A[1:4])  # 不会输出索引4的数

# What exactly is "iterable"?
for item in A[2:5]:
    print(item)
A = [1, 2]
A.append('2')
print(A)
A[0] = 's'
print(A)
print(list('abc') )

# 输出如下所示：
"""
6
1
100
[2, 3, 4]

3
4
5
[1, 2, '2']
['s', 2, '2']
['a', 'b', 'c']
"""

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# Method
A = list((2, 1, 3))
print(A)
A.sort(reverse = True) # A的值发生了改变
print(A)
# Function
print(sorted(A))  # A的值没有改变
print(A)

# 输出如下所示：
"""
[2, 1, 3]
[3, 2, 1]
[1, 2, 3]
[3, 2, 1]
"""

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# Tuple
# Create Tuple
A = tuple([1, 2, 3, 2])
print(A)
print(A[0])
print(A[2:4])
print(A[:4])
print(A[::])
print(A[:-1])
B = tuple([1, 2, 3, 4])
print(B[::-1])

A[0] = 's'
print(A)

C = tuple()
print(C)
C = 1,
print(C)
D = (1)
print(type(D))


# 输出如下所示：
"""
(1, 2, 3, 2)
1
(3, 2)
(1, 2, 3, 2)
(1, 2, 3, 2)
(1, 2, 3)
(4, 3, 2, 1)

A[0] = 's'
TypeError: 'tuple' object does not support item assignment

()
(1,)
<class 'int'>
"""

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# Set
A = set([1, 1, 2])
B = set(['Michal', 'Betty'])
print(A)
print(len(A))
print(B)
print(len(B))

C = set([1], [2])
print(C)

# Set Arithmetics
A = set([1, 2, 3])
B = set([3, 4, 5])
print('A intersects B')
print(A & B)
print('A unions B') 
print(A | B)
print('in A not in B')
print(A - B)
print('add 5 into A')
A.add(5)
print(A)
print('new A after adding 5')
print(A)
print('remove 2 in A')
A.remove(2)
print(A)
print('new A after reoving 2')
print(A)

# 输出如下所示：
"""
{1, 2}
2
{'Michal', 'Betty'}
2

C = set([1], [2])
TypeError: set expected at most 1 arguments, got 2

A intersects B
{3}
A unions B
{1, 2, 3, 4, 5}
in A not in B
{1, 2}
add 5 into A
{1, 2, 3, 5}
new A after adding 5
{1, 2, 3, 5}
remove 2 in A
{1, 3, 5}
new A after reoving 2
{1, 3, 5}
"""

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# Use tuple for demonstration here
A = (1, 2, 3)
print(len(A))

for item in A:
    print(item)

print(1 in A)

# 输出如下所示：
"""
3
1
2
3
True
"""

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# Dictionary
def simple_function(a, b, c):
    print(a)
    print(b)
    print(c)

simple_function(1, 2, 3)
simple_function(c = 3, a = 1, b = 2)
simple_function(1, c = 3, b = 2)

# 输出如下所示：
"""
1
2
3
1
2
3
1
2
3
"""

#### Create List 创建list
midterm1 = {'Michael': 98, 'Betty': 96}
print(midterm1)

final = dict() # 一个空字典
print(final)

midterm2 = dict(Michael = 98, Betty = 96)
print(midterm2)

midterm3 = dict([('Michael', 98), ('Betty', 96)])
print(midterm3)

print(midterm1 == midterm2 == midterm3)

midterm4 = dict([('Michael', 98), ('Betty', 96), ('Michael', 90)])
print(midterm4)

midterm1['Michael'] = 97
print(midterm1)

for key in midterm1:
    print(key)

print(midterm1.keys())
print(midterm1.values())

# 输出如下所示：
{'Michael': 98, 'Betty': 96}
{}
{'Michael': 98, 'Betty': 96}
{'Michael': 98, 'Betty': 96}
True
{'Michael': 90, 'Betty': 96}
{'Michael': 97, 'Betty': 96}
Michael
Betty
dict_keys(['Michael', 'Betty'])
dict_values([97, 96])

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# Ranges
print(list(range(10)))
print(list(range(0, 10, 3)))
print(list(range(0, -10, -1)))
print(list(range(0)))
print(list(range(1, 0)))

r = range(10)
print(5 in r)
print(r[1])

# 输出如下所示：
"""
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[0, 3, 6, 9]
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
[]
[]
True
1
"""

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# Hashable
print(hash('apple'))
print(hash(((1, -1, 0), (1, 0, 0), (1, 0, -1))))
print(hash(((1, 0, -1), (1, 0, 0), (1, -1, 0))))

# 输出如下所示：
-4061574024490551516
-697649482279922733
-697649482279922733

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# If Statement
name = 'Kesci'
if name == 'Kesci':
    print(name)

tool = 'Klab'
if tool != 'Kesci':
    print(tool)
    
# Use Good Grammar for Efficiency
# if if if
# if elif else
number = 10
def print_silly(x):
    if number == 10:
        print('checking the first one')
        print('equal to 10')
    if number <= 10:
        print('checking the second one')
        print('no less than 10')
    if number >= 10:
        print('checking the third one')
        print('no more than 10')

def print_clever(x):
    if number == 10:
        print('checking the first one')
        print('equal to 10')
    elif number <= 10:
        print('checking the second one')
        print('no less than 10')
    elif number >= 10:
        print('checking the third one')
        print('no more than 10')

print_silly(10)
print_clever(10)
    
 
# 输出如下所示：
"""
Kesci
Klab

checking the first one
equal to 10
checking the second one
no less than 10
checking the third one
no more than 10

checking the first one
equal to 10
"""

# For Loop
# When you know when to stop 当你知道你什么时候停止
count = 0
for number in range(10):
    count = count + number
    print(count)
    
# 输出如下所示：
"""
0
1
3
6
10
15
21
28
36
45
"""

# While loop
# Interchangeable with for loop 可以和for loop互换
# Must use this one if you don't know when to stop 当你不知道什么时候停下来
# Easy to have bug( forever looping) if you forget to modify your condition 容易有bug
unknown_condition = 100
my_number = 10
while my_number < unknown_condition:
    my_number = my_number + 10
    print(my_number)

print('I am out of while loop now')
print(my_number)

# 输出如下所示：
"""
20
30
40
50
60
70
80
90
100
I am out of while loop now
100
"""

# Nest your if statement in your loops:
# Use indentation
unknown_condition = 100
my_number = 0
while my_number < unknown_condition:
    if my_number % 2 == 0:
        my_number = my_number + 10
        print(my_number)
    else:
        my_number = my_number + 5
        print(my_number)

print('I am out of while loop now')
print('my_number is %d in the end'%my_number)

# 输出如下所示：
"""
10
20
30
40
50
60
70
80
90
100
I am out of while loop now
my_number is 100 in the end
"""

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A = [1,2]
B = A[:]
print(B)

print(B is A)

A = [[1,2,3],[4,5,6]]
B = A[:]
print(A)
print(B)

B[1][2] = 100
print(B)

print(A)

print(A is B)
print(A[0] is B[0])
print(A[1] is B[1])

# 输出如下所示：
"""
[1, 2]
False
[[1, 2, 3], [4, 5, 6]]
[[1, 2, 3], [4, 5, 6]]
[[1, 2, 3], [4, 5, 100]]
[[1, 2, 3], [4, 5, 100]]
False
True
True
"""

[[1, 2, 3], [4, 5, 100]]
[[1, 2, 3], [4, 5, 6]]
[[1, 2, 3], [4, 5, 100]]
# We call B a shallow copy of A, to make a deep copy,
# we need to use the copy.deepcopy function
import copy
A = [[1,2,3],[4,5,6]]
B = copy.copy(A)
B[1][2] = 100
print(A) # same as [:]

A = [[1,2,3],[4,5,6]]
B = copy.deepcopy(A)
B[1][2] = 100
print(A)
print(B)

# 输出如下所示：
"""
[[1, 2, 3], [4, 5, 100]]
[[1, 2, 3], [4, 5, 6]]
[[1, 2, 3], [4, 5, 100]]
"""