Python 数据类型之字符串，,Python 数据类

Python 数据类型之字符串，,Python 数据类

格式化字符串    参数替换(类的对象，方法调用，返回一个字符串)    >>> username = ‘root‘    >>> password = ‘foxconn168!‘    >>> "{0}‘s password is {1}".format(username,password)   --> 类的对象方法调用    "root‘s password is foxconn168!"    --> 返回一个字符串复合字段名    使用列表作为参数，可通过列表下标索引访问其元素    使用字典作为参数，可通过键来访问键值    使用模块作为参数，可通过名字访问变量和函数    使用类作为参数，可通过名字访问方法和属性    以上参数可任意组合    >>> a_list = [1,2,3,4,5,6]       -->  使用列表作为参数    >>> ‘6 * {0[0]} = {0[5]}‘.format(a_list)   --> {0[0}] 第一个参数的第一个元素    ‘6 * 1 = 6‘    >>>    >>> a_dict = {Name:Sam,Age:18}     --> 使用字典作为参数    >>> "{0[Name]}‘s age is {0[Age]}".format(a_dict)  --> {0[0}] 第一个参数的第一个元素    "Sam‘s age is 18"格式说明符    ‘{0:.1f} {1}‘.format(size, suffix)        --> {0:0.1f} 0 为第一个参数;:为格式说明符;.1f为四舍五入到1位        --> {1} 为第二个参数    >>> a_dict    {‘Name‘: ‘Sam‘, ‘Age‘: 18, ‘heigh‘: 65.55}    >>> "{0[Name]}‘s heigh is {0[heigh]:.1f}KG.".format(a_dict)    "Sam‘s heigh is 65.5KG."其他字符串操作    s.splitlines() --> 按行区分    s.lower()   --> 小写字符转换    s.count()  --> 字符个数统计    >>> s = ‘‘‘Instance attribute dictionaries are avoided by creating    ... class-level descriptors that intercept slot name access,and map    ... those names to sequential storage apace in the instance.‘‘‘    >>> s.splitlines()  -->  按行区分，返回列表    [‘Instance attribute dictionaries are avoided by creating ‘, ‘class-level descriptors that intercept slot name access,and map‘, ‘those names to sequential storage apace in the instance.‘]    >>> s.lower()   --> 小写字符转换    ‘instance attribute dictionaries are avoided by creating \nclass-level descriptors that intercept slot name access,and map\nthose names to sequential storage apace in the instance.‘    >>> print(s.lower())    instance attribute dictionaries are avoided by creating    class-level descriptors that intercept slot name access,and map    those names to sequential storage apace in the instance.    >>> s.lower().count(‘s‘)   --> 字符‘s‘出现的个数    14    >>>字符串转换为字典    >>> info = ‘name - sam / program - python / time - 2018‘    >>> info_list = info.split(‘ / ‘)    >>> print(info_list)    [‘name - sam‘, ‘program - python‘, ‘time - 2018‘]    >>> in_info_list = [x.split(‘ - ‘) for x in info_list]    >>> print(in_info_list)    [[‘name‘, ‘sam‘], [‘program‘, ‘python‘], [‘time‘, ‘2018‘]]    >>> a_dict = dict(in_info_list)    >>> print(a_dict)    {‘name‘: ‘sam‘, ‘program‘: ‘python‘, ‘time‘: ‘2018‘}字符串分片    类似列表分片,返回一个新的字串    >>> a_string = ‘Beginning Python:using Python 3.x.‘    >>> a_string[0:5]    ‘Begin‘    >>> a_string[:10]    ‘Beginning ‘    >>> a_string[5:-5]    ‘ning Python:using Python‘    >>> a_string[:-5]    ‘Beginning Python:using Python‘    >>> a_string[9:]    ‘ Python:using Python 3.x.‘string  VS  bytes    string:一个不可变(immutable)的unicode编码的字符序列    bytes:一串由0 - 255 之间的数字序列组成的bytes 对象(ASCII 或是\x00 - \xff)          bytes 对象是不可变的，可将bytes 对象转换为bytearray对象进行赋值(必须为0到255中的整数)          可通过 + 连接bytes对象          可通过下标取值(返回一个0到255中的整数)或len()计算bytes对象长度    >>> bt = b‘acd‘     --> bytes 定义    >>> type(bt)    <class ‘bytes‘>    >>> bt = b‘acd‘ + b‘\x98‘   --> bytes 使用 + 连接    >>> bt    b‘acd\x98‘    >>> bt = b‘acd‘ + b‘b‘    >>> bt    b‘acdb‘    >>> bt = bt + b‘\x99‘    >>> bt    b‘acdb\x99‘    >>> len(bt)                 -->  bytes 对象长度计算    5    >>> bt[0]                   --> 通过索引下标取bytes对象的值    97    >>> bt[0] = 100             --> 不能直接对bytes对象赋值    Traceback (most recent call last):      File "<stdin>", line 1, in <module>    TypeError: ‘bytes‘ object does not support item assignment    >>> btrr = bytearray(bt)    --> 将bytes对象转换为bytearray对象    >>> btrr[0]    97    >>> btrr[0] = 100           --> 对bytearray对象直接赋值    >>> btrr    bytearray(b‘dcdb\x99‘)    >>> bt    b‘acdb\x99‘    >>> type(btrr)              --> bytearray对象的类型    <class ‘bytearray‘>    >>> len(btrr)    5    >>> type(btrr)    <class ‘bytearray‘>string 和bytes 相互转换    string      encode      bytes    bytes       decode      string    >>> a_string = ‘學習python‘    >>> len(a_string)    8    >>> by = a_string.encode(‘utf-8‘)    >>> by    b‘\xe5\xad\xb8\xe7\xbf\x92python‘    >>> len(by)    12    >>> by = a_string.encode(‘big5‘)    >>> by    b‘\xbe\xc7\xb2\xdfpython‘    >>> len(by)    10    >>> roundtrip = by.decode(‘big5‘)    >>> roundtrip    ‘學習python‘    >>> roundtrip == a_string    True

Python 数据类型之字符串