PY习题

PY

网址
https://www.liaoxuefeng.com/wiki/0014316089557264a6b348958f449949df42a6d3a2e542c000

函数式编程

map/reduce

1.

def normalize(name):
    return str.capitalize(name)

2.

    def cheng(x,y):
        return x*y
    return reduce(cheng,L)

3.

    n = len(s)
    a = -1
    for i in range(n):
        a += 1
        if s[i] == '.':
            break
#‘a’为小数点位置
    def fn(x, y):
        return x * 10 + y
    def char2num(s):
        return {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}[s]
#基本函数
    s1 = ''
    s2 = ''
    for i in range(a):
        s1 = s1 + s[i]
    for i in range(n-a-1):
        s2 = s2 + s[i+a+1]
#重建无小数点数
    S = s1 + s2
    return reduce(fn, map(char2num, S))/(10**a)

Filter

1.

    L = str(n)
    a = len(L)
    b = 0
    for i in range(a):
        if L[i] == L[a-i-1]:
            b += 1
    return a == b

#原来切片能这么玩
    a = str(n)
    b = a[::-1]
    return a == b

sorted

1.

    for i in t:
        if isinstance(i,str):
            return i.lower() 

2.

def by_score(t):
    for i in t:
        if isinstance(i,int):
            return(i)
L2 = sorted(L, key=by_score,reverse=True)

面向对象高级编程

使用@property

    @property
    def width(self):
        return self._width
    @width.setter
    def width(self,value):
        self._width = value
    @property
    def height(self):
        return self._height
    @height.setter
    def height(self,value):
        self._height = value
    @property
    def resolution(self):
        return self._width*self._height

常用内建模块

datetime

    dt_dt = datetime.strptime(dt_str, '%Y-%m-%d %H:%M:%S')
    tz_match = re.match('^UTC([+-])(\d+):(\d+)', tz_str)
    tz = int(tz_match.group(1)+str(int(tz_match.group(2))))
    tz_utc_aim = timezone(timedelta(hours=tz))
    aim_dt = dt_dt.replace(tzinfo=tz_utc_aim)
    dt_ts = aim_dt.timestamp()
    return dt_ts

base64

    if isinstance(s,str) == True:
        a = len(s) % 4
        if a == 0:
            return base64.b64decode(s)
        else:
            return base64.b64decode(s + '='*(4-a))
    else:
        s_str = s.decode('ascii')
        b = len(s_str) % 4
        if b == 0:
            return base64.b64decode(s_str)
        else:
            return base64.b64decode(s_str + '='*(4-b))

#原来bytes可以这么玩
    return base64.b64decode(s + b'=' * (4 - len(s) % 4))

#原来join可以这么玩
    d = [s]
    m = len(s) % 4
    for i in range(m):
        d.append(b'=')
    return base64.b64decode(b''.join(d))

hashlib

1.密码 -> MD5

import hashlib
def calc_md5(password):
    md5 = hashlib.md5()
    md5.update(password.encode('utf-8'))
    return md5.hexdigest()

2.验证密码

import hashlib
db = {
    'michael': 'e10adc3949ba59abbe56e057f20f883e',
    'bob': '878ef96e86145580c38c87f0410ad153',
    'alice': '99b1c2188db85afee403b1536010c2c9'
}
def login(user,password):
    md5 = hashlib.md5()
    md5.update(password.encode('utf-8'))
    pw_md5 = md5.hexdigest()
    if pw_md5 == db[user]:
        print('Ture')
    else:
        print('False')

3.加盐加用户名

import hashlib
db = {}
def register(user, password):
    safe_password = password + user + 'the-Salt'
    md5 = hashlib.md5()
    md5.update(safe_password.encode('utf-8'))
    get_md5 = md5.hexdigest()
    db[user] = get_md5
def login(user,password):
    safe_password = password + user + 'the-Salt'
    md5 = hashlib.md5()
    md5.update(safe_password.encode('utf-8'))
    pw_md5 = md5.hexdigest()
    if pw_md5 == db[user]:
        print('Ture')
    else:
        print('False')   

访问数据库

使用SQLite

    conn = sqlite3.connect(db_file)
    cursor = conn.cursor()
    cursor.execute('select * from user')
    values = cursor.fetchall()
    cursor.close()
    conn.close()
    name = []
    def by_score(t):
        for i in t:
            if isinstance(i,int):
                return(i)
    L = sorted(values, key=by_score)
    for i in range(len(L)):
        if isinstance(i,int) and low <= L[i][2] <= high:
            name.append(L[i][1])
    return name

#原来SQL有这种操作
    connect = sqlite3.connect(db_file)
    cursor_score = connect.cursor()
    cursor_score.execute('select name from user where score>=? and score<=? order by score', (low, high))
    values = cursor_score.fetchall()
    cursor_score.close()
    connect.close()
    return [value[0] for value in values]