Python教程3 - 复习：内置对象

>>> id(1)  # 这个数字是会改变的
139698536331168
>>> type(1) is int  # 最好不要在此处使用 ==
True
>>> a = [1, 2, 3]
>>> b = [1, 2, 3]
>>> a == b
True
>>> a is b  # 对于相同值的可变对象，它们也可能不是同一对象，拥有不同的ID
False
>>> a is not b  # 上面式子的否定
True
>>> isinstance(1, int)
True
>>> isinstance('1', int)
False
>>> isinstance(1, object)
True
>>> isinstance('1', object)
True
>>> issubclass(int, object)
True

>>> int(0.9)
0
>>> int(-0.9)
0
>>> int('177')
177
>>> int('177', 8)
127
>>> int('0o177', base=0)
127

>>> str(127)
'127'
>>> bin(127)
'0b1111111'
>>> oct(127)
'0o177'
>>> hex(127)
'0x7f'
>>> hex(127)[2:]  # 如果你不想要进制标识，可以用切片语法去除掉
'7f'

>>> 0.1 + 0.1 + 0.1 == 0.3
False

>>> import math
>>> math.isclose(0.1 + 0.1 + 0.1, 0.3)
True

>>> +0
0
>>> -0    # 整数只有一种0
0
>>> +0.0
0.0
>>> -0.0  # 浮点数有两种0
-0.0
>>> +0.0 == -0.0  # 但这两种0是相等的。
True

>>> 1e1000
inf
>>> float('inf')
inf
>>> import numpy
>>> numpy.float64(1) / 0.0
<stdin>:1: RuntimeWarning: divide by zero encountered in double_scalars
inf
>>> 1.0 / 0.0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ZeroDivisionError: float division by zero

>>> inf = float('inf')
>>> inf / inf
nan
>>> nan = float('nan')
>>> nan == nan
False

>>> 'It\'s me.'
"It's me."
>>> "It's me."
"It's me."
>>> '''And then,
... that's you'''
"And then,\nthat's you"

>>> print('1\t2\n3\t4')
1       2
3       4
>>> '\x0a' == '\n' # 换行符ASCII码为10，十六进制为0a
True

>>> ord('我')
25105
>>> chr(25105)
'我'

>>> text = '你好世界'
>>> binary = text.encode()
>>> binary
b'\xe4\xbd\xa0\xe5\xa5\xbd\xe4\xb8\x96\xe7\x95\x8c'
>>> binary.decode()
'你好世界'

>>> print(str('1\t2'))
1       2
>>> print(repr('1\t2'))
'1\t2'

>>> print("1\t2".__str__())
1       2
>>> print("1\t2".__repr__())
'1\t2'

>>> '1234'.startswith('12')
True
>>> '1234'.endswith('12')
False
>>> '1234'.find('23')
1
>>> '1234'.find('32')
-1

>>> 'abc'.upper()
'ABC'
>>> '  a\tb\t '.strip()
'a\tb'

>>> items = '1\t 2\n3'.split()
>>> items
['1', '2', '3']
>>> ','.join(items)
'1,2,3'

>>> list1 = [1, 2, 3, 4]
>>> list2 = [
...     'one',
...     'two',
...     'three',
...     'four',
... ]
>>> empty = []
>>> mono = ['a']

>>> (1, 2, 3)
(1, 2, 3)
>>> (1)  # 错误的单元素元组表示方法
1
>>> (1,)
(1,)
>>> ()   # 空元组
()

>>> a = [3, 4]
>>> b = [1, 2, *a, *(5, 6), 7]
>>> b
[1, 2, 3, 4, 5, 6, 7]

>>> a = 1, 2
>>> a
(1, 2)
>>> b, c = 3, 4
>>> b
3
>>> c
4
>>> b, c = c, b  # 交换两个变量

>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> tuple(range(10))
(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)

>>> [*range(5), *range(3)]
[0, 1, 2, 3, 4, 0, 1, 2]
>>> import itertools
>>> list(itertools.chain(range(5), range(3)))
[0, 1, 2, 3, 4, 0, 1, 2]

>>> iterable = [1, 2]
>>> iterator = iter(iterable)
>>> next(iterator)
1
>>> next(iterator)
2
>>> next(iterator)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
>>> iterator = iter(iterable)
>>> iterator is iter(iterator)
True

>>> a = list(range(5, 10))  # 产生一个5到9的列表
>>> a
[5, 6, 7, 8, 9]
>>> import random
>>> random.shuffle(a)  # 随机打乱这个列表
>>> a
[5, 9, 7, 6, 8]
>>> min(a)
5
>>> max(a)
9
>>> sum(a)
35
>>> list(enumerate(a))  # 由于enumerate返回的是迭代器，所以需要list来转换为列表，下同
[(0, 5), (1, 9), (2, 7), (3, 6), (4, 8)]
>>> for i, v in enumerate(a):  # 这个是enumerate经常被使用的方式
...   print(str(i) + ': ' + str(v))
...
0: 5
1: 9
2: 7
3: 6
4: 8
>>> list(filter(lambda x: x > 6, a))  # 筛选出列表中大于6的元素
[9, 7, 8]
>>> list(map(lambda x: x * 2, a))  # 将列表中所有元素乘以2
[10, 18, 14, 12, 16]
>>> all(map(lambda x: x > 5, a))  # 测试是否所有元素都大于5
False
>>> any(map(lambda x: x > 5, a))  # 测试是否存在元素大于5
True
>>> list(zip(range(5, 10), range(10, 5, -1)))
[(5, 10), (6, 9), (7, 8), (8, 7), (9, 6)]

>>> s, t = list(range(5)), list(range(5, 10))
>>> s
[0, 1, 2, 3, 4]
>>> t
[5, 6, 7, 8, 9]
>>> 5 in s
False
>>> 5 not in s
True
>>> s + t
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> s * 2
[0, 1, 2, 3, 4, 0, 1, 2, 3, 4]
>>> s[-1]
4
>>> s[::-1]  # 一种颠倒序列的方式
[4, 3, 2, 1, 0]
>>> len(s)
5
>>> list(reversed(s))  # 另一种颠倒序列的方式
[4, 3, 2, 1, 0]
>>> s.index(3)
3
>>> s.count(1)
1

>>> s = list(range(5))
>>> s
[0, 1, 2, 3, 4]
>>> s[0] = 5
>>> s
[5, 1, 2, 3, 4]
>>> s[1:3] = [2, 1]
>>> s
[5, 2, 1, 3, 4]
>>> s[::-1] = s  # 一种原处颠倒序列的方法，和 s[:] = s[::-1] 以及 s.reverse() 等价
>>> s
[4, 3, 1, 2, 5]
>>> del s[::2]  # 删除下标是偶数的元素
>>> s
[3, 2]
>>> s.append(6)
>>> s
[3, 2, 6]
>>> s += [7, 8]
>>> s
[3, 2, 6, 7, 8]
>>> s *= 2
>>> s
[3, 2, 6, 7, 8, 3, 2, 6, 7, 8]
>>> s.pop()
8
>>> s
[3, 2, 6, 7, 8, 3, 2, 6, 7]
>>> s.remove(8)
>>> s
[3, 2, 6, 7, 3, 2, 6, 7]
>>> s.reverse()
>>> s
[7, 6, 2, 3, 7, 6, 2, 3]

>>> s = [[0]] * 3
>>> s
[[0], [0], [0]]
>>> s[0][0] = 1
>>> s
[[1], [1], [1]]

>>> s = [[0] for _ in range(3)]
>>> s
[[0], [0], [0]]
>>> s[0][0] = 1
>>> s
[[1], [0], [0]]

>>> fruits = ['orange', 'apple', 'banana']
>>> fruits_sorted = fruits[:]
>>> fruits_sorted.sort()  # 普通的排序方法
>>> fruits_sorted
['apple', 'banana', 'orange']
>>> fruits_with_index = list(enumerate(fruits))  # argsort的排序方法
>>> fruits_with_index
[(0, 'orange'), (1, 'apple'), (2, 'banana')]
>>> fruits_with_index.sort(key=lambda x: x[1])
>>> fruits_with_index
[(1, 'apple'), (2, 'banana'), (0, 'orange')]
>>> fruits_argsorted = list(map(lambda x: x[0], fruits_with_index))
>>> fruits_argsorted  # argsort排序完成，得到的结果就是数字。数组是从小到大各个元素的下标
[1, 2, 0]

>>> squares = []
>>> for x in range(10):
...     squares.append(x**2)
...
>>> squares
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

squares = list(map(lambda x: x**2, range(10)))

squares = [x**2 for x in range(10)]

>>> [(x, y) for x in [1,2,3] for y in [3,1,4] if x != y]
[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]

>>> combs = []
>>> for x in [1,2,3]:
...     for y in [3,1,4]:
...         if x != y:
...             combs.append((x, y))
...
>>> combs
[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]

>>> matrix = [
...     [1, 2, 3, 4],
...     [5, 6, 7, 8],
...     [9, 10, 11, 12],
... ]
>>> [[row[i] for row in matrix] for i in range(4)]
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]

>>> transposed = []
>>> for i in range(4):
...     transposed.append([row[i] for row in matrix])
...
>>> transposed
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]

>>> transposed = []
>>> for i in range(4):
...     # the following 3 lines implement the nested list comprehension
...     transposed_row = []
...     for row in matrix:
...         transposed_row.append(row[i])
...     transposed.append(transposed_row)
...
>>> transposed
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]

>>> {'a': 1, 1: 'a', ('1', 1): 'a'}
{'a': 1, 1: 'a', ('1', 1): 'a'}
>>> {
...   'a': 1,  # 末尾可以跟逗号
... }
{'a': 1}
>>> {['1', 1]: 'a'}  # 列表不是可哈希对象
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
>>> {}  # 空的字典
{}

>>> a = {'a': 0, 'b': 1}
>>> b = {**a, 'a': 1}  # 解包
>>> b
{'a': 1, 'b': 1}
>>> {1: 'a', 1.0: 'b'}  # 由于 1 == 1.0 ，后面的键值对会替代前面的
{1: 'b'}

>>> a = {'a': 0, 'b': 1}
>>> dict(a, a=1)
{'a': 1, 'b': 1}
>>> dict([('a', 0), ('b', 1), ('c', 2)])
{'a': 0, 'b': 1, 'c': 2}
>>> dict(zip(['a', 'b', 'c'], range(3)))
{'a': 0, 'b': 1, 'c': 2}

>>> d = {'a': 1, 'b': 2}
>>> len(d)
2
>>> list(d)  # 等价于list(d.keys())
['a', 'b']
>>> d['c'] = 3
>>> d
{'a': 1, 'b': 2, 'c': 3}
>>> del d['a']
>>> d
{'b': 2, 'c': 3}
>>> 'a' in d
False
>>> d == {'c': 3, 'b': 2}  # 可以看出顺序并不影响是否相等
True
>>> list(d.items())
[('b', 2), ('c', 3)]
>>> list(d.values())
[2, 3]
>>> d.get('d', 4)
4
>>> d.pop('c', 5)
3
>>> d
{'b': 2}
>>> d.update([('a', 1), ('c', 3)])
>>> d.popitem()  # 最后插入的是('c', 3)，所以它被pop了出来
('c', 3)
>>> d
{'b': 2, 'a': 1}
>>> d.clear()
>>> d
{}
>>> d.setdefault('a', 0)
0
>>> d
{'a': 0}
>>> d.copy()
{'a': 0}

>>> dishes = {'eggs': 2, 'sausage': 1, 'bacon': 1, 'spam': 500}
>>> keys = dishes.keys()
>>> values = dishes.values()

>>> # 迭代，会调用iter(values)
>>> n = 0
>>> for val in values:
...     n += val
>>> print(n)
504

>>> # keys和values按照同样的顺序（插入顺序）
>>> list(keys)
['eggs', 'sausage', 'bacon', 'spam']
>>> list(values)
[2, 1, 1, 500]

>>> # 视图对象是动态的，会反映字典的变化
>>> del dishes['eggs']
>>> del dishes['sausage']
>>> list(keys)
['bacon', 'spam']

>>> # 集合操作
>>> keys & {'eggs', 'bacon', 'salad'}
{'bacon'}
>>> keys ^ {'sausage', 'juice'}
{'juice', 'sausage', 'bacon', 'spam'}

>>> {x: x**2 for x in (2, 4, 6)}
{2: 4, 4: 16, 6: 36}

>>> {1, 3, 2}          # 集合元素迭代的顺序不一定遵循插入顺序
{1, 2, 3}
>>> {1, 1, 3.0, 3, 2}  # 集合会去除掉重复的元素
{1, 2, 3.0}

>>> a = [1, 2, 3]
>>> b = [2, 3, 4]
>>> {*a, *b}
{1, 2, 3, 4}

>>> a = {1, 3, 2}
>>> [2 * i for i in a]
[2, 4, 6]
>>> tuple(a)
(1, 2, 3)

>>> a = [1, 2, 3, 2, 1]
>>> set(a)
{1, 2, 3}
>>> frozenset(a)
frozenset({1, 2, 3})

>>> a = [1, 2, 3, 2, 1]
>>> list(set(a))         # 一个典型的去重操作
[1, 2, 3]

>>> a = {1, 2, 3}
>>> b = {2, 3, 4}
>>> c = {1, 2, 3, 4}
>>> len(c)
4
>>> a.isdisjoint(b)
False
>>> a < c                 # 真子集
True
>>> a & b                 # 交
{2, 3}
>>> a ^ b                 # 对称差
{1, 4}
>>> c.intersection(a, b)  # a、b和c的交集
{2, 3}

>>> a = {1, 2, 3}
>>> b = {4, 5}
>>> a |= b
>>> a
{1, 2, 3, 4, 5}
>>> a.add(7)
>>> a.discard(6)
>>> a.remove(6)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 6
>>> a.pop()
1
>>> a
{2, 3, 4, 5, 7}
>>> a.clear()
>>> a
set()

>>> {x**2 for x in (2, 4, 6)}
{16, 4, 36}

>>> 1 + 1j  # 产生复杂复数的方法
(1+1j)
>>> complex(1, 2)
(1+2j)

>>> a = 1 + 2j
>>> abs(a)  # 求模
2.23606797749979
>>> a.real  # 取实部
1.0
>>> a.imag  # 取虚部
2.0
>>> a.conjugate() # 求共轭复数

Please input the first real number: 1.2
Please input the second real number: 2.3
1.2 + 2.3 = 3.5

if __name__ == '__main__':
    a = float(input('Please input the first real number: '))
    b = float(input('Please input the second real number: '))
    print(str(a) + ' + ' + str(b) + ' = ' + str(a + b))

Please input a real number: -1
-1.0 is a negative number

if __name__ == '__main__':
    number = float(input('Please input a real number: '))
    if number > 0.0:
        print(str(number) + ' is a positive number')
    elif number < 0.0:
        print(str(number) + ' is a negative number')
    else:
        print(str(number) + ' is zero')

Please input a real number (input 0 to stop): 2
Please input a real number (input 0 to stop): 1
Please input a real number (input 0 to stop): 3
Please input a real number (input 0 to stop): 0
The maximum number is 3.0
The minimum number is 1.0
The average number is 2.0
The sum number is 6.0

if __name__ == '__main__':
    numbers = []
    while True:
        number = float(input('Please input a real number (input 0 to stop): '))
        if number == 0:
            break
        numbers.append(number)
    if numbers:
        print('The maximum number is ' + str(max(numbers)))
        print('The minimum number is ' + str(min(numbers)))
        sum_of_numbers = sum(numbers)
        print('The average number is ' + str(sum_of_numbers / len(numbers)))
        print('The sum number is ' + str(sum_of_numbers))
    else:
        print('You entered a empty sequence')

import math

if __name__ == '__main__':
    max1, min1, sum1, n = -math.inf, math.inf, 0.0, 0
    while True:
        number = float(input('Please input a real number (input 0 to stop): '))
        if number == 0:
            break
        max1 = max(max1, number)
        min1 = min(min1, number)
        sum1 += number
        n += 1
    if n:
        print('The maximum number is ' + str(max1))
        print('The minimum number is ' + str(min1))
        print('The average number is ' + str(sum1 / n))
        print('The sum number is ' + str(sum1))
    else:
        print('You entered a empty sequence')

Please input a line: aba
It is a palindrome

if __name__ == '__main__':
    line = input('Please input a line: ')
    if line == line[::-1]:
        print('It is a palindrome')
    else:
        print('It is not a palindrome')

if __name__ == '__main__':
    line = input('Please input a line: ')
    for a, b in zip(line, reversed(line)):
        if a != b:
            print('It is not a palindrome')
            break
    else:
        print('It is a palindrome')

if __name__ == '__main__':
    line = input('Please input a line: ')
    for a, b, _ in zip(line, reversed(line), range(len(line) // 2)):
        if a != b:
            print('It is not a palindrome')
            break
    else:
        print('It is a palindrome')

Please input a line: a1h45
Number of alphas is 2
Number of digits is 3

if __name__ == '__main__':
    line = input('Please input a line: ')
    n_alpha, n_digit = 0, 0
    for char in line:
        if char.isalpha():
            n_alpha += 1
        elif char.isdigit():
            n_digit += 1
    print('Number of alphas is ' + str(n_alpha))
    print('Number of digits is ' + str(n_digit))

Please input a line: what the fuck does what the fuck mean
does: 1
fuck: 2
mean: 1
the: 2
what: 2

if __name__ == '__main__':
    line = input('Please input a line: ')
    words = line.split()
    counter = {}
    for word in words:
        counter[word] = counter.get(word, 0) + 1
    for key, value in sorted(counter.items()):
        print(str(key) + ': ' + str(value))

Please input a number: 6
6
3
10
5
16
8
4
2
1

if __name__ == '__main__':
    num = int(input('Please input a number: '))
    while True:
        print(num)
        if num == 1:
            break
        elif num % 2 == 0:
            num //= 2
        else:
            num = 3 * num + 1

def power(x, n):
    # Your need to call power inside this function
    pass


if __name__ == '__main__':
    x = int(input('Please input the base: '))
    n = int(input('Please input the exponent: '))
    print(str(x) + '^' + str(n) + ' = ' + str(power(x, n)))

Please input the base: 2
Please input the exponent: 5
2^5 = 32

def power(x, n):
    if n == 0:
        return 1
    elif n % 2:
        return x * power(x * x, (n - 1) // 2)
    else:
        return power(x * x, n // 2)


if __name__ == '__main__':
    x = int(input('Please input the base: '))
    n = int(input('Please input the exponent: '))
    print(str(x) + '^' + str(n) + ' = ' + str(power(x, n)))

Please input the first line: how are you today
Please input the second line: how old are you
old

pip install numpy matplotlib

import numpy as np
import matplotlib.pyplot as plt

MAX_ITER = 256


def mandelbrot(c):
    # TODO
    pass


def main():
    resolution = 512
    c = np.linspace(-2, 1, resolution)[np.newaxis, :] \
        + 1j * np.linspace(-1.5, 1.5, resolution)[:, np.newaxis]
    result = np.vectorize(mandelbrot)(c)
    plt.imshow(np.log(result + 1))
    plt.show()


if __name__ == '__main__':
    main()