Python: Exercise Examples

  1. 从低位依次打印,并计算位数
    复制代码
    n = int(input('number: '))
count = 0

while True:
    print(n % 10)
    n = n // 10
    count += 1
    if n == 0:
        break
print('number of digits: ', count)
    复制代码

     

  2. 从高位依次打印(必须先得到位数)
    复制代码
    n = int(input('number: '))
count = 0

if n > 1000:
    if n > 10000:
        count = 5
    else:
        count = 4
else:
    if n > 100:
        count = 3
    elif n > 10:
        count = 2
    else:
        count = 1

print('digits: {0}'.format(count))

prev = 0
for i in range(count, 0, -1):
    curr = n // (10 ** (i - 1))
    print(curr - prev * 10)
    prev = curr
    复制代码

     

  3. 求1-5 factorial 和
    复制代码
    sum = 0
for i in range(1, 6):
    n = 1
    for j in range(1, i + 1):
        n *= j
    sum += n
else:
    print(sum)

tmp = 1
# method 2
sum = 0
for i in range(1, 6):
    tmp *= i
    sum += tmp
else:
    print(sum)
    复制代码

     

  4. prime number

  5. 九九乘法表
    for i in range(1,10):
  for j in range(1,i+1):
    print('{1} * {0} = {2}\t'.format(i,j,i*j),end='')
  print()
    复制代码
    for i in range(1,10):
  for j in range(1,i+1):
    product=i*j
    if j>1 and product<10:
      product=str(product)+' '
    else:
      product=str(product)
    print(str(j)+'*'+str(i)+'='+product,end=' ')
  print()
    复制代码
    for i in range(1,10):
  line=''
  for j in range(1,i+1):
    line+='{0}*{1}={2:<2} '.format(j,i,i*j)
  print(line)

     

    for i in range(1, 10):
  line = ''
  for j in range(1, 10):
    if j < i:
      line += ' ' * 7
    else:
      line += '{}*{}={:<2} '.format(i, j, i * j)
  print(line)
    for i in range(1, 10):
  print(' ' * 7 * (i - 1), end='')  # print space 
  for j in range(i, 10):
    print('{0}*{1}={2:<2} '.format(i, j, i * j), end='')
  print()

     

  6. 打印 rhombus
    复制代码
    for i in range(-3, 4):
  if i < 0:
    prespace = -i
  else:
    prespace = i
  print(' ' * prespace + '*' * (7 - 2 * prespace))

  
for i in range(-3, 4):
  prespace = i if i >= 0 else -i
  print(' ' * prespace + '*' * (7 - 2 * prespace))
    复制代码

     

    for i in range(-3, 4):
  print(' ' * abs(i) + '*' * (7 - 2 * abs(i)))

     

    复制代码
    for i in range(-3, 4):
  if i < 0:
    prev = abs(i)
    post = 3
  elif i == 0:
    prev = post = 0
  else:
    prev = 3
    post = i
  print(' ' * prev + '*' * (7 - prev - post))
  
for i in range(-3,4):
  if i==0:
    print('*'*7)
  print(' '*abs(i)+'*'*(4-abs(i))) if i<0 else print(' '*3+'*'*(3-i))
    复制代码

     

  7. 倒序打印输入字符, 并统计出现次数
    复制代码
    while True:
    n = input('>').strip().lstrip('0')
    if n.isdecimal():
        break
    else:
        print('{} format wrong'.format(n))

counter = [0] * 10

for b in range(10):
    counter[b] = n.count(str(b))

for b in range(10):
    if counter[b]:
        print(f'{b} counts: {counter[b]}')

lst = list(n)
lst.reverse()
print(''.join(lst))
    复制代码

     

  8. 打印Fibonacci小于100项
    复制代码
    b, p = 0, 1

print(p)
while True:
    c = b + p
    if c > 100:
        break
    print(c)
    b = p
    p = c
    复制代码

    求Fibonacci第10项

    复制代码
    # Loop 1
b, p = 0, 1

for i in range(9):
    b, p = p, b + p
else:
    print(p)

# Loop 2
b, p = 0, 1
count = 0
while True:
    b, p = p, b + p
    count += 1
    if count == 9:
        break
print(p)


# Recursive 1
def fibonacci(n):
    if n < 2:
        return n
    return fibonacci(n - 1) + fibonacci(n - 2)


print(fibonacci(10))


# Tail Resursive
def fibonacci(n, prev, next):
    if n == 1:
        return next
    return fibonacci(n - 1, next, prev + next)


print(fibonacci(10, 0, 1))
    复制代码

     

  9. 求1000内的prime number
    复制代码
    count = 0
lst1 = []
lst2 = []
for i in range(2, 1000 + 1):
    for j in range(2, i):
        if i % j == 0:
            break
    else:
        count += 1
        lst1.append(i)
print(count)

count = 1  # add 2
# int(i**0.5)+1, 9, 15, 35
for i in range(3, 1000 + 1, 2):
    for j in range(3, int(i ** 0.5) + 1, 2):
        if i % j == 0:
            break
    else:
        count += 1

print(count)

count = 2
for i in range(3, 1000 + 1, 2):
    tmp = i ** 0.5
    for j in range(3, i, 2):
        if i % j == 0:
            break
        if j > tmp:
            count += 1
            lst2.append(i)
            break

print(count)

for i in lst1:
    if i not in lst2:
        print(i)
    复制代码
    复制代码
    import math

n = 100
primes = []
for x in range(2, n + 1):
    for i in primes:
        if x % i == 0:
            break
    else:
        primes.append(x)

print(len(primes))

primes.clear()

for x in range(2, n + 1):
    flag = True
    for p in primes:
        if x % p == 0:
            flag = False
            break
        if p == math.ceil(math.sqrt(x)):
            print(p, x)
        if p > math.ceil(math.sqrt(x)):
            break
    if flag:
        primes.append(x)

print(len(primes))
    复制代码

     

  10. 猴子吃桃
    复制代码
    n = 1
for i in range(9):
    n = (n + 1) * 2
else:
    print(n)


def peach(n):
    if n == 10:
        return 1
    return peach(n + 1) * 2 + 2


print(peach(1))
    复制代码
    复制代码
    n = 1
c = 0
# while True:
#     c += 1
#     n = (n + 1) * 2
#     if c == 9:
#         break

while True:
    if c == 9:  # 0-9，c==9，第十次没有执行循环
        break
    c += 1
    n = (n + 1) * 2
print(n)
    复制代码

     

  11. 杨辉三角
    复制代码
    triangle = []

for i in range(6):
    vex = []
    triangle.append(vex)
    for j in range(i + 1):
        if j == 0 or j == i:
            vex.append(1)
            # print(i, j, triangle, vex)
        else:
            # print(i, j, triangle, vex)
            vex.append(triangle[i - 1][j - 1] + triangle[i - 1][j])
print(triangle)
    复制代码

     

     

  12.  transport matric 转置矩阵

     

     

    复制代码
    vex = list(range(1, 10))
vie = []

tmp = []
for i in vex:
    tmp.append(i)
    if i % 3 == 0:
        vie.append(tmp)
        tmp = []

print(vie)

for i in range(len(vie)):
    for j in range(len(vie[i])):
        print(vie[j][i], end=' ')
    print()
    复制代码

     

    复制代码
    vex = list(range(1, 10))
vie = []

tmp = []
for i in vex:
    tmp.append(i)
    if i % 3 == 0:
        vie.append(tmp)
        tmp = []

print(vie)

# 对角线 i=j,非对角线i>j或i<j, 只需交换一边
for i in range(len(vie)):
    for j in range(i):  # i>j
        vie[j][i], vie[i][j] = vie[i][j], vie[j][i]

print(vie)

for i in range(len(vie)):
    for j in range(i + 1, len(vie)):  # i<j
        vie[j][i], vie[i][j] = vie[i][j], vie[j][i]

print(vie)

for i, row in enumerate(vie):
    for j, elem in enumerate(row):
        if i < j:
            vie[j][i], vie[i][j] = vie[i][j], vie[j][i]

print(vie)
    复制代码

     

     

    复制代码
    vie = [[1, 2, 3], [4, 5, 6]]
vole = []

for i, row in enumerate(vie):
    for j, v in enumerate(row):
        if i == 0:
            vole.append([v])
        else:
            vole[j].append(v)

print(vole)

vole = []
for row in vie:
    for i, v in enumerate(row):
        if len(vole) < i + 1:
            vole.append([])
        vole[i].append(v)

print(vole)

vole = [[0 for i in range(len(vie))] for _ in range(len(vie[0]))]
for i, row in enumerate(vie):
    for j, v in enumerate(row):
        vole[j][i] = vie[i][j]

print(vole)
    复制代码

     

  13. 随机生成10个数字,统计重复和不重复个数
    复制代码
    import random

n = []
for _ in range(10):
    n.append(random.randrange(21))

print(n)

same = []
diff = []

states = [0] * len(n)

for i in range(len(n)):
    flag = False
    if states[i]:
        continue

    for j in range(i + 1, len(n)):
        if states[j]:
            continue
        if n[i] == n[j]:
            flag = True
            states[j] = 1
    if flag:
        same.append(n[i])
        states[i] = 1
    else:
        diff.append(n[i])

print(same, diff)
    复制代码

     

  14. set 集合

     

     

    复制代码
    import random

s1 = set()
s2 = set()
for _ in range(10):
    s1.add(random.randrange(10, 21))
    s2.add(random.randrange(10, 21))
print(s1, s2)
print(f'common: {len(s1 | s2)}')
print(f'unique: {len(s1 ^ s2)}')
print(f'duplicate: {s1 & s2}')
    复制代码

     

  15. 简单选择排序
    复制代码
    import random

vixen = list(range(10))
random.shuffle(vixen)
print(vixen)

count_iter = count_swap = 0
for i in range(len(vixen)):
    min_index = i
    for j in range(i + 1, len(vixen)):
        count_iter += 1
        if vixen[min_index] > vixen[j]:
            min_index = j

    if i != min_index:
        count_swap += 1
        vixen[i], vixen[min_index] = vixen[min_index], vixen[i]

print(vixen)
print(count_iter)
print(count_swap)
    复制代码

    二元选择排序

    复制代码
    import random

vixen = list(range(10))
random.shuffle(vixen)
print(vixen)

count_iter = count_swap = 0

for i in range(len(vixen) // 2):  # len(vixen)=odd: len(vixen)//2 自然被排好序
    minindex = i
    maxindex = -i - 1  # 与minindex对称
    maxorigin = maxindex
    for j in range(i + 1, len(vixen) - i):  # 负索引也对称
        count_iter += 1
        if vixen[minindex] > vixen[j]:
            minindex = j
        if vixen[maxindex] < vixen[-j - 1]:
            maxindex = -j - 1  # not j

        if vixen[minindex] == vixen[maxindex]:  # 剩余元素相同
            break

        if i != minindex:
            vixen[i], vixen[minindex] = vixen[minindex], vixen[i]
            count_swap += 1

        if maxorigin != maxindex and vixen[maxorigin] != vixen[maxindex]:  # 2 2 2 2 1 情况
            vixen[maxorigin], vixen[maxindex] = vixen[maxindex], vixen[maxorigin]
            count_swap += 1
print(vixen)
print(count_iter)
print(count_swap)
    复制代码

     

    b = ['{:>04}.{}'.format(n, ''.join((random.choice(string.ascii_lowercase) for _ in range(5)))) for n in range(5)]
    b = ['{:04}.{}'.format(n, ''.join((chr(random.randint(97, 122)) for _ in range(5)))) for n in range(5)]

     

    ['{:04}.{}'.format(n, ''.join((random.choice(bytes(range(97, 123)).decode()) for _ in range(10)))) for n in range(1, 101)]

     

  16. 生成随机captcha
    复制代码
    import random


def captcha(size=7):
    res = ''
    for i in range(size):
        lowercase = chr(random.randint(97, 122))
        uppercase = chr(random.randrange(65, 91))
        number = chr(random.randrange(48, 58))
        res += random.choice((lowercase, uppercase, number))
    return res


print(captcha(8))
    复制代码

     

  17. 列表解析式打印九九乘法表
    [print('{}*{}={:<3}{}'.format(j, i, i * j, '\n' if i == j else ' '), end=' ') for i in range(1, 10) for j in
 range(1, i + 1)]

     

  18.  

     

    复制代码
    while True:
    n = input('>>').strip().lstrip('0')
    if n.isdecimal():
        break
    else:
        print('{} wrong'.format(n))
d = {}
for b in n:
    if b not in d.keys():
        d[b] = 0
    d[b] += 1

# for b in n:
#     d[b] = d.get(b, 0) + 1

# for b in n:
#     if d.get(b, None):
#         d[b] += 1
#     else:
#         d.setdefault(b, 1)

for b in n:
    print(f'number: {b}, count: {d[b]}')
    复制代码

     

  19.  

     

    import random


def vivify(*nums):
    return max(nums), min(nums)


print(*vivify(*(random.randrange(10, 30) for _ in range(50))))

     

     

    复制代码
    def vocal(n):
    for i in range(1, 13):
        for j in range(12, 0, -1):
            if j <= i:
                print('{:<{width}}'.format(j, width=1 if j == 1 else 3), end='')
            else:
                print(' ' * 3, end='')
        print()

    print()

    for i in range(12, 0, -1):
        for j in range(12, 0, -1):
            if j <= i:
                print('{:<{width}}'.format(j, width=1 if j == 1 else 3), end='')
            else:
                print(' ' * 3, end='')
        print()


vocal(13)
    复制代码
    复制代码
    def vivify(n):
    tail = ' '.join((str(i) for i in range(n, 0, -1)))

    width = len(tail)

    for i in range(1, n):
        print('{:>{}}'.format(' '.join((str(i) for i in range(i, 0, -1))), width))
    print(tail)

    print()
    
    print(tail)
    for i in range(n - 1, 0, -1):
        print('{:>{}}'.format(' '.join((str(i) for i in range(i, 0, -1))), width))


vivify(13)
    复制代码
    复制代码
    def vivify(n):
    head = ' '.join(((str(i) for i in range(n, 0, -1))))
    print(head)

    for i in range(len(head)):  # 空格分隔
        if head[i] == ' ':
            print(' ' * i, head[i + 1:], sep=' ')


vivify(13)
    复制代码

     

  20. 直接插入排序
    复制代码
    import random

nums = list(range(10))
random.shuffle(nums)

print(nums)


def insert_sort(vixen):
    count_assign = 0
    vixen = [0] + vixen

    for i in range(2, len(vixen)):
        vixen[0] = vixen[i]  # sentinel, 待插入值
        j = i - 1
        while vixen[j] > vixen[0]:
            count_assign += 1
            vixen[j + 1] = vixen[j]
            j -= 1

        vixen[j + 1] = vixen[0]
    print(count_assign)
    return vixen[1:]


print(insert_sort(nums))
    复制代码

     

  21. 将数字倒序生成list
    复制代码
    def vixen(n, l=None):
    if l is None:
        l = []
    if n // 10:
        l.append(n % 10)
        return vixen(n // 10, l)
    l.append(n)
    return l


print(vixen(1234))


def vixen(n, target=None):
    if target is None:
        target = []
    x, y = divmod(n, 10)
    target.append(y)
    if x == 0:
        return target
    return vixen(x, target)

print(vixen(12345))

def vixen(n, target=[]):
    if n:
        target.append(int(n[-1]))
        vixen(n[:-1])
    return target


print(vixen(str(1234)))


def vixen(n):
    def vixen_(i):
        if i == -1:
            return ''
        return str(n)[i] + vixen_(i - 1)

    res = vixen_(len(str(n)) - 1)
    return [int(x) for x in res]


print(vixen(12345))
    复制代码

     　　

  22. 猴子吃桃
    复制代码
    def peach(n):
    if n == 10:
        return 1
    return peach(n + 1) * 2 + 2


print(peach(1))


def peach(n, res=1):
    if n < 0:
        return -1
    if n == 10:
        return res
    res = res * 2 + 2
    return peach(n + 1, res)


print(peach(1))
    复制代码

     

  23. 生成器实现febonacci
    复制代码
    def febonacci():
    b = 0
    p = 1
    while True:
        yield p
        b, p = p, b + p


r = febonacci()
for _ in range(5):
    print(next(r))
    复制代码

     

  24. 实现built-in函数sorted功能
    复制代码
    import random

vale = list(range(10))
random.shuffle(vale)


def sort(iterable, reverse=False):
    ret = []

    # def comp()

    for item in iterable:
        for i, v in enumerate(ret):
            # if item > v if reverse else item < v:
            #     ret.insert(i, item)
            #     break
            if reverse:
                if item > v:
                    ret.insert(i, item)
                    break
            else:
                if item < v:
                    ret.insert(i, item)
                    break
        else:
            ret.append(item)

    return ret


print(vale)
print(sort(vale, True))
print(sort(vale, 0))
    复制代码

    抽离函数

    复制代码
    def sort(iterable, reverse=False):
    ret = []

    def comp(v, item, reverse):
        return item > v if reverse else item < v

    for item in iterable:
        for i, v in enumerate(ret):
            if comp(v, item, reverse):
                ret.insert(i, item)
                break
        else:
            ret.append(item)

    return ret
    复制代码

     

    复制代码
    import random

vale = list(range(10))
random.shuffle(vale)


def comp(a, b):
    return a < b


def sort(iterable, key=lambda a, b: a < b, reverse=False):
    ret = []

    for item in iterable:
        for i, v in enumerate(ret):
            flag = key(v, item) if reverse else key(item, v)
            if flag:
                ret.insert(i, item)
                break
        else:
            ret.append(item)

    return ret


print(vale)
print(sort(vale, key=comp, reverse=True))
print(sort(vale, key=comp, reverse=False))
print(sort(vale))
    复制代码

     

  25. 字典flat

     

    复制代码
    bud = {'a': {'b': 11, 'c': 'tt'}, 'd': {'e': 3, 'f': {'g': 55}}}


def flat(d: dict, target=None, prefix=''):
    if target is None:
        target = {}
    for k, v in d.items():
        # if type(v) == dict:
        if isinstance(v, (dict,)):
            flat(v, target, prefix=prefix + k + '.')
        else:
            target[prefix + k] = v
    if prefix == '':
        return target


print(flat(bud))
    复制代码

     

  26. 实现base64.b64encode()

    复制代码
    import string, base64


def encode(s):
    alphabet = string.ascii_uppercase + string.ascii_lowercase + string.digits + '+' + '/'
    alphabet = bytes(alphabet, encoding='utf8')
    ret = bytearray()
    zeros = 0
    length = len(s)
    for offset in range(0, length, 3):
        if offset + 3 <= length:  # 可取到源数据的三个有效字节
            triple = s[offset:offset + 3]
        else:
            # zeros = 3 - (length - offset)
            # triple = s[offset:] + b'\x00' * zeros
            triple = s[offset:]
            zeros = 3 - len(triple)
            triple = triple + b'\x00' * zeros

        n = int.from_bytes(triple, 'big')  # 对n进行移位

        for i in range(18, -1, -6):  # 右移四次,18 12 6 0
            if i == 18:
                index = n >> i
            else:
                index = n >> i & 0x3F

            ret.append(alphabet[index])

            print(ret)

        for i in range(zeros):
            ret[-i - 1] = 0x3D  # bytearray每个元素0-255整形, = 码值0x3D

            print(zeros)
    return bytes(ret)


s = 'abcd'
print(encode(s.encode(encoding='utf8')))
print(base64.b64encode(s.encode()))
    复制代码

     

  27. 求最长字串

    复制代码
    s1 = 'abcdefg'
s2 = 'defabcdoabcdeftw'
s3 = '='


def find_substr(s1: str, s2: str):
    if len(s1) > len(s2):
        s1, s2 = s2, s1

    count = 0
    length = len(s1)

    for sublen in range(length, 0, -1):
        for start in range(0, length - sublen + 1):
            substr = s1[start:start + sublen]
            count += 1

            if s2.find(substr) > -1:
                print('count={}'.format(count))
                return substr

    return ''


print(find_substr(s1, s2))
print(find_substr(s1, s3))
    复制代码
    复制代码
    s1 = 'abcdefg'
s2 = 'defabcdoabcdeftw'


def find_substr(s1: str, s2: str):
    if len(s1) > len(s2):
        s1, s2 = s2, s1
    length = len(s1)

    matrix = []
    max = 0  # 最大字串长度
    xindex = 0  # 最大字串结束索引(s2)
    yindex = 0
    for i, v1 in enumerate(s1):  # 外层循环从小串开始
        matrix.append([])
        for j, v2 in enumerate(s2):
            if v1 == v2:
                if i == 0 or j == 0:  # i==0(s1[0]) j==0(s2[0])
                    matrix[i].append(1)
                else:
                    matrix[i].append(matrix[i - 1][j - 1] + 1)
            else:
                matrix[i].append(0)
            if matrix[i][j] > max:
                max = matrix[i][j]
                xindex = j
                yindex = i

    return s1[yindex - max + 1:yindex + 1], s2[xindex - max + 1:xindex + 1]  # xindex+1因为后开, xindex-xmax+1,因为直接减字串长度,会多往前走一个


print(find_substr(s2, s1))
    复制代码

     

  28.  随机数生成器

    复制代码
    import random


class RandomGenerator:
    def __init__(self, n=10, minimum=1, maximum=10):
        self.n = n
        self.minimum = minimum
        self.maximum = maximum
        self.g = self._generator()

    def _generator(self):
        while True:
            yield [random.randint(self.minimum, self.maximum) for _ in range(self.n)]

    def generator(self, n=15):
        self.n = n
        return next(self.g)


r = RandomGenerator()
print(r.generator(5))
print(r.generator(10))
print(r.generator())
    复制代码

     

  29.  

    温度转换类
     

    复制代码
    class Temperature:
    def __init__(self, t, unit='c'):
        '''
        description
        :param t:
        :param unit:
        :return None
        '''
        self.__celsius = None
        self.__fahrenheit = None
        self.__kelvin = None

        if unit == 'k':
            self.__kelvin = t
            self.__celsius = self.k2c(t)

        elif unit == 'f':
            self.__celsius = self.f2c(t)
            self.__fahrenheit = t
        else:
            self.__celsius = t

    @property
    def kelvin(self):
        if self.__kelvin is None:
            self.__kelvin = self.c2k(self.__celsius)
        return self.__kelvin

    @property
    def celsius(self):
        return self.__celsius

    @property
    def fahrenheit(self):
        if self.__fahrenheit is None:
            self.__fahrenheit = self.c2f(self.__celsius)
        return self.__fahrenheit

    @classmethod
    def c2f(cls, c):
        return c * 9 / 5 + 32

    @classmethod
    def f2c(cls, f):
        return (f - 32) * 5 / 9

    @classmethod
    def c2k(cls, c):
        return c + 273.15

    @classmethod
    def k2c(cls, k):
        return k - 273.15

    @classmethod
    def k2f(cls, k):
        return cls.c2f(cls.k2c(k))

    @classmethod
    def f2k(cls, f):
        return cls.c2k(cls.f2c(f))
    复制代码

     

  30. class __call__ Fibonacci
    复制代码
    class Fibonacci:
    def __init__(self):
        self.vagary = [0, 1]

    def __len__(self):
        return len(self.vagary)

    def __call__(self, index):
        if index < 0:
            raise IndexError(f'{index} out of range')
        if index <= len(self):
            return self.vagary[index]
        else:
            for i in range(len(self) - 1, index):
                self.vagary.append(self.vagary[i - 1] + self.vagary[i])
            return self.vagary[index]

    def __getitem__(self, index):
        if index < 0:
            return None
        if index <= len(self):
            return self.vagary[index]
        else:
            self(index)
            return self.vagary[index]

    def __iter__(self):
        self.__g = iter(self.vagary)
        return self

    def __next__(self):
        return next(self.__g)

    def __repr__(self):
        return str(self.vagary)

    __str__ = __repr__


f = Fibonacci()

print(f(5))
print(f)
for v in f:
    print(v)
print(f.vagary)
print(f(7))
print(f.vagary)
print(f(3))
print(f[55])
print(f.vagary)
    复制代码

     

  31. 上下文管理

     

     

    复制代码
    import sys


class Point:
    def __init__(self):
        print('__init__')

    def __enter__(self):
        print(f'__enter__ {self.__class__}')
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        print(f'__exit__ {self.__class__.__name__}')
        print(f'exc_type {exc_type}')
        print(f'exc_val {exc_val}')
        print(f'exc_tb {exc_tb}')
        # return True  # stifle Exception


p = Point()
print(f'p = {p}')
with p as f:
    raise Exception('Error')
    sys.exit(202)
    print(f'f = {f}')

print('end')
    复制代码

     

  32. 时间计数器
    复制代码
    import time, datetime


class Chronograph:
    def __init__(self):
        pass

    def __enter__(self):
        self.start = datetime.datetime.now()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        print((datetime.datetime.now() - self.start).total_seconds())


def add(x, y):
    time.sleep(1.5)
    return x + y


with Chronograph() as f:
    add(5, 55)
    复制代码
    复制代码
    import time, datetime
from functools import wraps


def chronograph(f):
    @wraps(f)
    def wrapper(*args, **kwargs):
        start = datetime.datetime.now()
        ret = f(*args, **kwargs)
        delta = (datetime.datetime.now() - start).total_seconds()
        print(f'{f.__name__} elapsed {delta}')
        return ret

    return wrapper


@chronograph
def add(x, y):
    time.sleep(1.5)
    return x + y


add(5, 55)
    复制代码

     

  33. 实现staticmethod classmethod
    复制代码
    from functools import wraps, partial


class StaticMethod:
    def __init__(self, f):
        self.f = f

    def __get__(self, instance, owner):
        print(f'{self.__class__.__name__} {self, instance, owner}')
        return self.f


class ClassMethod:
    def __init__(self, f):
        self.f = f

    def __get__(self, instance, owner):
        print(f'{self.__class__.__name__} {self, instance, owner}')

        # @wraps(self.f)
        # def wrapper(*args, **kwargs):
        #     return self.f(owner, *args, **kwargs)

        # return wrapper
        return partial(self.f, owner)


class B:
    @StaticMethod
    def vagary():
        print(f'vagary')

    @ClassMethod
    def vague(cls, b, /):
        '''
        __doc__
        :param b:
        :return:
        '''
        print(cls.__name__, b)


print(B.__dict__)
print(B.vagary, type(B.vagary))
B.vagary()
B.vague(55)
print(B.vague.__doc__)
    复制代码

     

  34. 对类进行类型检查
    复制代码
    import inspect


class CheckMode:
    def __init__(self, name, mold):
        self.name = name
        self.mold = mold

    def __get__(self, instance, owner):
        if instance is not None:  # Instance Call
            return instance.__dict__[self.name]  # Not JS
        return self

    def __set__(self, instance, value):  # Only instance call __set__
        if isinstance(value, self.mold):
            instance.__dict__[self.name] = value
        else:
            raise TypeError(f'{value} is not {self.mold}')


# def type_assert(cls):
#     parameters = inspect.signature(cls).parameters
#     print(parameters)
#     for arg, parameter in parameters.items():
#         print(arg, parameter, type(parameter))
#         if parameter.annotation != parameter.empty:
#             setattr(cls, arg, CheckMode(arg, parameter.annotation))
#     return cls


# @type_assert
class TypeAssert:
    def __init__(self, cls):
        self.cls = cls
        self.__assert()

    def __assert(self):
        parameters = inspect.signature(self.cls).parameters
        for arg, parameter in parameters.items():
            if parameter.annotation != parameter.empty:
                setattr(self.cls, arg, CheckMode(arg, parameter.annotation))

    def __call__(self, *args, **kwargs):
        return self.cls(*args, **kwargs)


@TypeAssert
class Person:
    def __init__(self, name: str, age: int):
        # parameters = ((name, str), (age, int))
        # if not self.check_mode(parameters):
        #     raise TypeError()
        self.name = name
        self.age = age

    def check_mode(self, parameters):
        for var, mode in parameters:
            if not isinstance(var, mode):
                return False
        return True


print(Person.__dict__)
print(type(Person), Person.cls.__dict__)
p = Person('r', 5)
# p = Person('r', '5')
    复制代码

     

  35. 实现内置property
    复制代码
    class Property:
    def __init__(self, fget, fset=None, fdel=None):
        self.fget = fget
        self.fset = fset
        self.fdel = fdel

    def __get__(self, instance, owner):
        if not instance:
            return self
        return self.fget(instance)

    def __set__(self, instance, value):
        if callable(self.fset):
            self.fset(instance, value)
        else:
            AttributeError(f'{self.fset} not callable')

    def __delete__(self, instance):
        self.fdel(instance)

    def setter(self, fset):
        self.fset = fset
        return self

    def deleter(self, fdel):
        self.fdel = fdel
        return self


class B:
    def __init__(self, data):
        self._data = data

    @Property
    def data(self):
        return self._data

    @data.setter
    def data(self, value):
        self._data = value

    @data.deleter
    def data(self):
        del self._data


b = B(5)
b.data = 55
print(b.data)
del b.data
print(b.__dict__)
print(B.__dict__)
    复制代码

     

  36. 转换到int
    def cast2int(v):
    try:
        return int(v)
    except:
        return 0


print(toInt('b'))

     

  37. 多线程print函数(线程不安全)

     

     print不换行

    复制代码
    import threading, time


def b():
    for x in range(100):
        print(f'{threading.current_thread()} running\n', end='')


for x in range(5):
    threading.Thread(target=b, name=f'work-{x}').start()
    复制代码

    logging module

    复制代码
    import threading, time, logging

logging.basicConfig(level=logging.INFO)


def b():
    for x in range(100):
        logging.info(f'{threading.current_thread().name} running')


for x in range(5):
    threading.Thread(target=b, name=f'work-{x}').start()
    复制代码

     

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