Python（变量、数据类型）
2024-08-27 19:16:16
常量：
python中没有常量，只能通过名字特征来提示
例如：
全部大写，如 ： OLDBOY_AGE=57
一.变量
变量
声明变量
#!/usr/bin/env python age=18
gender1='male'
gender2='female' 变量作用：保存状态（程序的运行本质是一系列状态的变化，变量的目的就是用来保存状态，变量值的变化就构成了程序运行的不同结果。）
例如：CS枪战，一个人的生命可以表示为life＝active表示存活，当满足某种条件后修改变量life＝inactive表示死亡。
- 变量命名规则遵循标识符命名规则，详见第二篇
- name＝'lhf':'lhf'才是内存变量，name只是内存变量的引用
- 与c的区别在于变量赋值操作无返回值
- 链式赋值：y＝x＝a＝1
- 多元赋值：x,y=1,2 x,y=y,x
- 增量赋值：x+=1
二.数据类型
2.1 什么是数据类型及数据类型分类
程序的本质就是驱使计算机去处理各种状态的变化，这些状态分为很多种 例如英雄联盟游戏，一个人物角色有名字，钱，等级，装备等特性，大家第一时间会想到这么表示
名字：德玛西亚－－－－－－－－－－－－>字符串
钱：10000 －－－－－－－－－－－－>数字
等级：15 －－－－－－－－－－－－>数字
装备：鞋子，日炎斗篷，兰顿之兆－－－－>列表
(记录这些人物特性的是变量，这些特性的真实存在则是变量的值，存不同的特性需要用不同类型的值) python中的数据类型
python使用对象模型来存储数据，每一个数据类型都有一个内置的类，每新建一个数据，实际就是在初始化生成一个对象，即所有数据都是对象
对象三个特性
- 身份：内存地址，可以用id()获取
- 类型：决定了该对象可以保存什么类型值，可执行何种操作，需遵循什么规则，可用type()获取
- 值：对象保存的真实数据
注：我们在定义数据类型，只需这样：x＝1，内部生成1这一内存对象会自动触发，我们无需关心 这里的字符串、数字、列表等都是数据类型（用来描述某种状态或者特性）除此之外还有很多其他数据，处理不同的数据就需要定义不同的数据类型
| 标准类型 | 其他类型 |
| 数字 | 类型type |
| 字符串 | Null |
| 列表 | 文件 |
| 元组 | 集合 |
| 字典 | 函数／方法 |
| 类 | |
| 模块 |
2.2 标准数据类型：
2.2.1 数字
定义：a＝1
特性：
1.只能存放一个值
2.一经定义，不可更改
3.直接访问
分类：整型，长整型，布尔，浮点，复数
2.2.1.1 整型:
Python的整型相当于C中的long型,Python中的整数可以用十进制,八进制,十六进制表示。
>>> 10
10 --------->默认十进制
>>> oct(10)
'012' --------->八进制表示整数时，数值前面要加上一个前缀“0”
>>> hex(10)
'0xa' --------->十六进制表示整数时，数字前面要加上前缀0X或0x
python2.*与python3.*关于整型的区别
python2.*
在32位机器上，整数的位数为32位，取值范围为-2**31～2**31-1，即-2147483648～2147483647 在64位系统上，整数的位数为64位，取值范围为-2**63～2**63-1，即-9223372036854775808～9223372036854775807
python3.*整形长度无限制
2.2.1.2 长整型long：
python2.*：
跟C语言不同，Python的长整型没有指定位宽，也就是说Python没有限制长整型数值的大小，
但是实际上由于机器内存有限，所以我们使用的长整型数值不可能无限大。
在使用过程中，我们如何区分长整型和整型数值呢？
通常的做法是在数字尾部加上一个大写字母L或小写字母l以表示该整数是长整型的，例如：
a = 9223372036854775808L
注意，自从Python2起，如果发生溢出，Python会自动将整型数据转换为长整型，
所以如今在长整型数据后面不加字母L也不会导致严重后果了。 python3.*
长整型，整型统一归为整型
python2.7
>>> a=9223372036854775807
>>> a
>>> a+=1
>>> a
9223372036854775808L python3.5
>>> a=9223372036854775807
>>> a
>>> a+=1
>>> a 查看
'''
# print(type(n))
# print(type(f)) # print(1.3e-3)
# print(1.3e3) # print(bin(10)) #二进制
# print(oct(10)) #八进制
# # 0-9 a b c d e f
# print(hex(10)) #16进制
''' #数字类型的特点：
# 1.只能存放一个值
#
# 2.一经定义，不可更改，更改的是变量和值的对应关系
#
# 3.直接访问
# x=10123123123
# print(id(x))
# x=11
# print(id(x))
# print(id(11))
#====================运行结果：=====================
# D:\Python36\python.exe D:/py/train.py
#
#
#
# Process finished with exit code 0
#================================================
2.2.1.3 布尔bool:
True 和False
1和0
2.2.1.4 浮点数float:
Python的浮点数就是数学中的小数，类似C语言中的double。
在运算中，整数与浮点数运算的结果是浮点数
浮点数也就是小数，之所以称为浮点数，是因为按照科学记数法表示时，
一个浮点数的小数点位置是可变的，比如，1.23*109和12.3*108是相等的。
浮点数可以用数学写法，如1.23，3.14，-9.01，等等。但是对于很大或很小的浮点数，
就必须用科学计数法表示，把10用e替代，1.23*109就是1.23e9，或者12.3e8，0.000012
可以写成1.2e-5，等等。
整数和浮点数在计算机内部存储的方式是不同的，整数运算永远是精确的而浮点数运算则可能会有
四舍五入的误差。
2.2.1.5 复数complex:
复数由实数部分和虚数部分组成，一般形式为x＋yj，其中的x是复数的实数部分，y是复数的虚数部分，这里的x和y都是实数。
注意，虚数部分的字母j大小写都可以，
>>> 1.3 + 2.5j == 1.3 + 2.5J
True
2.2.1.6 数字相关内建函数
2.2.2 字符串
定义：它是一个有序的字符的集合，用于存储和表示基本的文本信息，‘’或“”或‘’‘ ’‘’中间包含的内容称之为字符串
特性：
1.只能存放一个值
2.不可变
3.按照从左到右的顺序定义字符集合，下标从0开始顺序访问，有序
补充：
1.字符串的单引号和双引号都无法取消特殊字符的含义，如果想让引号内所有字符均取消特殊意义，在引号前面加r，如name＝r'l\thf'
2.unicode字符串与r连用必需在r前面，如name＝ur'l\thf'
2.2.2.1 字符串创建
‘hello world’
2.2.2.2 字符串常用操作
移除空白
分割
长度
索引
切片
2.2.2.3 字符工厂函数str()
class str(object):
"""
str(object='') -> str
str(bytes_or_buffer[, encoding[, errors]]) -> str Create a new string object from the given object. If encoding or
errors is specified, then the object must expose a data buffer
that will be decoded using the given encoding and error handler.
Otherwise, returns the result of object.__str__() (if defined)
or repr(object).
encoding defaults to sys.getdefaultencoding().
errors defaults to 'strict'.
"""
def capitalize(self): # real signature unknown; restored from __doc__
"""
首字母变大写
S.capitalize() -> str Return a capitalized version of S, i.e. make the first character
have upper case and the rest lower case.
"""
return "" def casefold(self): # real signature unknown; restored from __doc__
"""
S.casefold() -> str Return a version of S suitable for caseless comparisons.
"""
return "" def center(self, width, fillchar=None): # real signature unknown; restored from __doc__
"""
原来字符居中，不够用空格补全
S.center(width[, fillchar]) -> str Return S centered in a string of length width. Padding is
done using the specified fill character (default is a space)
"""
return "" def count(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
从一个范围内的统计某str出现次数
S.count(sub[, start[, end]]) -> int Return the number of non-overlapping occurrences of substring sub in
string S[start:end]. Optional arguments start and end are
interpreted as in slice notation.
"""
return 0 def encode(self, encoding='utf-8', errors='strict'): # real signature unknown; restored from __doc__
"""
encode(encoding='utf-8',errors='strict')
以encoding指定编码格式编码，如果出错默认报一个ValueError，除非errors指定的是
ignore或replace S.encode(encoding='utf-8', errors='strict') -> bytes Encode S using the codec registered for encoding. Default encoding
is 'utf-8'. errors may be given to set a different error
handling scheme. Default is 'strict' meaning that encoding errors raise
a UnicodeEncodeError. Other possible values are 'ignore', 'replace' and
'xmlcharrefreplace' as well as any other name registered with
codecs.register_error that can handle UnicodeEncodeErrors.
"""
return b"" def endswith(self, suffix, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.endswith(suffix[, start[, end]]) -> bool Return True if S ends with the specified suffix, False otherwise.
With optional start, test S beginning at that position.
With optional end, stop comparing S at that position.
suffix can also be a tuple of strings to try.
"""
return False def expandtabs(self, tabsize=8): # real signature unknown; restored from __doc__
"""
将字符串中包含的\t转换成tabsize个空格
S.expandtabs(tabsize=8) -> str Return a copy of S where all tab characters are expanded using spaces.
If tabsize is not given, a tab size of 8 characters is assumed.
"""
return "" def find(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.find(sub[, start[, end]]) -> int Return the lowest index in S where substring sub is found,
such that sub is contained within S[start:end]. Optional
arguments start and end are interpreted as in slice notation. Return -1 on failure.
"""
return 0 def format(self, *args, **kwargs): # known special case of str.format
"""
格式化输出
三种形式：
形式一.
>>> print('{0}{1}{0}'.format('a','b'))
aba 形式二：（必须一一对应）
>>> print('{}{}{}'.format('a','b'))
Traceback (most recent call last):
File "<input>", line 1, in <module>
IndexError: tuple index out of range
>>> print('{}{}'.format('a','b'))
ab 形式三：
>>> print('{name} {age}'.format(age=12,name='lhf'))
lhf 12 S.format(*args, **kwargs) -> str Return a formatted version of S, using substitutions from args and kwargs.
The substitutions are identified by braces ('{' and '}').
"""
pass def format_map(self, mapping): # real signature unknown; restored from __doc__
"""
与format区别
'{name}'.format(**dict(name='alex'))
'{name}'.format_map(dict(name='alex')) S.format_map(mapping) -> str Return a formatted version of S, using substitutions from mapping.
The substitutions are identified by braces ('{' and '}').
"""
return "" def index(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.index(sub[, start[, end]]) -> int Like S.find() but raise ValueError when the substring is not found.
"""
return 0 def isalnum(self): # real signature unknown; restored from __doc__
"""
至少一个字符，且都是字母或数字才返回True S.isalnum() -> bool Return True if all characters in S are alphanumeric
and there is at least one character in S, False otherwise.
"""
return False def isalpha(self): # real signature unknown; restored from __doc__
"""
至少一个字符，且都是字母才返回True
S.isalpha() -> bool Return True if all characters in S are alphabetic
and there is at least one character in S, False otherwise.
"""
return False def isdecimal(self): # real signature unknown; restored from __doc__
"""
S.isdecimal() -> bool Return True if there are only decimal characters in S,
False otherwise.
"""
return False def isdigit(self): # real signature unknown; restored from __doc__
"""
S.isdigit() -> bool Return True if all characters in S are digits
and there is at least one character in S, False otherwise.
"""
return False def isidentifier(self): # real signature unknown; restored from __doc__
"""
字符串为关键字返回True S.isidentifier() -> bool Return True if S is a valid identifier according
to the language definition. Use keyword.iskeyword() to test for reserved identifiers
such as "def" and "class".
"""
return False def islower(self): # real signature unknown; restored from __doc__
"""
至少一个字符，且都是小写字母才返回True
S.islower() -> bool Return True if all cased characters in S are lowercase and there is
at least one cased character in S, False otherwise.
"""
return False def isnumeric(self): # real signature unknown; restored from __doc__
"""
S.isnumeric() -> bool Return True if there are only numeric characters in S,
False otherwise.
"""
return False def isprintable(self): # real signature unknown; restored from __doc__
"""
S.isprintable() -> bool Return True if all characters in S are considered
printable in repr() or S is empty, False otherwise.
"""
return False def isspace(self): # real signature unknown; restored from __doc__
"""
至少一个字符，且都是空格才返回True
S.isspace() -> bool Return True if all characters in S are whitespace
and there is at least one character in S, False otherwise.
"""
return False def istitle(self): # real signature unknown; restored from __doc__
"""
>>> a='Hello'
>>> a.istitle()
True
>>> a='HellP'
>>> a.istitle()
False S.istitle() -> bool Return True if S is a titlecased string and there is at least one
character in S, i.e. upper- and titlecase characters may only
follow uncased characters and lowercase characters only cased ones.
Return False otherwise.
"""
return False def isupper(self): # real signature unknown; restored from __doc__
"""
S.isupper() -> bool Return True if all cased characters in S are uppercase and there is
at least one cased character in S, False otherwise.
"""
return False def join(self, iterable): # real signature unknown; restored from __doc__
"""
#对序列进行操作（分别使用' '与':'作为分隔符）
>>> seq1 = ['hello','good','boy','doiido']
>>> print ' '.join(seq1)
hello good boy doiido
>>> print ':'.join(seq1)
hello:good:boy:doiido #对字符串进行操作 >>> seq2 = "hello good boy doiido"
>>> print ':'.join(seq2)
h:e:l:l:o: :g:o:o:d: :b:o:y: :d:o:i:i:d:o #对元组进行操作 >>> seq3 = ('hello','good','boy','doiido')
>>> print ':'.join(seq3)
hello:good:boy:doiido #对字典进行操作 >>> seq4 = {'hello':1,'good':2,'boy':3,'doiido':4}
>>> print ':'.join(seq4)
boy:good:doiido:hello #合并目录 >>> import os
>>> os.path.join('/hello/','good/boy/','doiido')
'/hello/good/boy/doiido' S.join(iterable) -> str Return a string which is the concatenation of the strings in the
iterable. The separator between elements is S.
"""
return "" def ljust(self, width, fillchar=None): # real signature unknown; restored from __doc__
"""
S.ljust(width[, fillchar]) -> str Return S left-justified in a Unicode string of length width. Padding is
done using the specified fill character (default is a space).
"""
return "" def lower(self): # real signature unknown; restored from __doc__
"""
S.lower() -> str Return a copy of the string S converted to lowercase.
"""
return "" def lstrip(self, chars=None): # real signature unknown; restored from __doc__
"""
S.lstrip([chars]) -> str Return a copy of the string S with leading whitespace removed.
If chars is given and not None, remove characters in chars instead.
"""
return "" def maketrans(self, *args, **kwargs): # real signature unknown
"""
Return a translation table usable for str.translate(). If there is only one argument, it must be a dictionary mapping Unicode
ordinals (integers) or characters to Unicode ordinals, strings or None.
Character keys will be then converted to ordinals.
If there are two arguments, they must be strings of equal length, and
in the resulting dictionary, each character in x will be mapped to the
character at the same position in y. If there is a third argument, it
must be a string, whose characters will be mapped to None in the result.
"""
pass def partition(self, sep): # real signature unknown; restored from __doc__
"""
以sep为分割，将S分成head,sep,tail三部分 S.partition(sep) -> (head, sep, tail) Search for the separator sep in S, and return the part before it,
the separator itself, and the part after it. If the separator is not
found, return S and two empty strings.
"""
pass def replace(self, old, new, count=None): # real signature unknown; restored from __doc__
"""
S.replace(old, new[, count]) -> str Return a copy of S with all occurrences of substring
old replaced by new. If the optional argument count is
given, only the first count occurrences are replaced.
"""
return "" def rfind(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.rfind(sub[, start[, end]]) -> int Return the highest index in S where substring sub is found,
such that sub is contained within S[start:end]. Optional
arguments start and end are interpreted as in slice notation. Return -1 on failure.
"""
return 0 def rindex(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.rindex(sub[, start[, end]]) -> int Like S.rfind() but raise ValueError when the substring is not found.
"""
return 0 def rjust(self, width, fillchar=None): # real signature unknown; restored from __doc__
"""
S.rjust(width[, fillchar]) -> str Return S right-justified in a string of length width. Padding is
done using the specified fill character (default is a space).
"""
return "" def rpartition(self, sep): # real signature unknown; restored from __doc__
"""
S.rpartition(sep) -> (head, sep, tail) Search for the separator sep in S, starting at the end of S, and return
the part before it, the separator itself, and the part after it. If the
separator is not found, return two empty strings and S.
"""
pass def rsplit(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__
"""
S.rsplit(sep=None, maxsplit=-1) -> list of strings Return a list of the words in S, using sep as the
delimiter string, starting at the end of the string and
working to the front. If maxsplit is given, at most maxsplit
splits are done. If sep is not specified, any whitespace string
is a separator.
"""
return [] def rstrip(self, chars=None): # real signature unknown; restored from __doc__
"""
S.rstrip([chars]) -> str Return a copy of the string S with trailing whitespace removed.
If chars is given and not None, remove characters in chars instead.
"""
return "" def split(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__
"""
以sep为分割，将S切分成列表，与partition的区别在于切分结果不包含sep，
如果一个字符串中包含多个sep那么maxsplit为最多切分成几部分
>>> a='a,b c\nd\te'
>>> a.split()
['a,b', 'c', 'd', 'e']
S.split(sep=None, maxsplit=-1) -> list of strings Return a list of the words in S, using sep as the
delimiter string. If maxsplit is given, at most maxsplit
splits are done. If sep is not specified or is None, any
whitespace string is a separator and empty strings are
removed from the result.
"""
return [] def splitlines(self, keepends=None): # real signature unknown; restored from __doc__
"""
Python splitlines() 按照行('\r', '\r\n', \n')分隔，
返回一个包含各行作为元素的列表，如果参数 keepends 为 False，不包含换行符，如 果为 True，则保留换行符。
>>> x
'adsfasdf\nsadf\nasdf\nadf'
>>> x.splitlines()
['adsfasdf', 'sadf', 'asdf', 'adf']
>>> x.splitlines(True)
['adsfasdf\n', 'sadf\n', 'asdf\n', 'adf'] S.splitlines([keepends]) -> list of strings Return a list of the lines in S, breaking at line boundaries.
Line breaks are not included in the resulting list unless keepends
is given and true.
"""
return [] def startswith(self, prefix, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.startswith(prefix[, start[, end]]) -> bool Return True if S starts with the specified prefix, False otherwise.
With optional start, test S beginning at that position.
With optional end, stop comparing S at that position.
prefix can also be a tuple of strings to try.
"""
return False def strip(self, chars=None): # real signature unknown; restored from __doc__
"""
S.strip([chars]) -> str Return a copy of the string S with leading and trailing
whitespace removed.
If chars is given and not None, remove characters in chars instead.
"""
return "" def swapcase(self): # real signature unknown; restored from __doc__
"""
大小写反转
S.swapcase() -> str Return a copy of S with uppercase characters converted to lowercase
and vice versa.
"""
return "" def title(self): # real signature unknown; restored from __doc__
"""
S.title() -> str Return a titlecased version of S, i.e. words start with title case
characters, all remaining cased characters have lower case.
"""
return "" def translate(self, table): # real signature unknown; restored from __doc__
"""
table=str.maketrans('alex','big SB') a='hello abc'
print(a.translate(table)) S.translate(table) -> str Return a copy of the string S in which each character has been mapped
through the given translation table. The table must implement
lookup/indexing via __getitem__, for instance a dictionary or list,
mapping Unicode ordinals to Unicode ordinals, strings, or None. If
this operation raises LookupError, the character is left untouched.
Characters mapped to None are deleted.
"""
return "" def upper(self): # real signature unknown; restored from __doc__
"""
S.upper() -> str Return a copy of S converted to uppercase.
"""
return "" def zfill(self, width): # real signature unknown; restored from __doc__
"""
原来字符右对齐，不够用0补齐 S.zfill(width) -> str Pad a numeric string S with zeros on the left, to fill a field
of the specified width. The string S is never truncated.
"""
return "" def __add__(self, *args, **kwargs): # real signature unknown
""" Return self+value. """
pass def __contains__(self, *args, **kwargs): # real signature unknown
""" Return key in self. """
pass def __eq__(self, *args, **kwargs): # real signature unknown
""" Return self==value. """
pass def __format__(self, format_spec): # real signature unknown; restored from __doc__
"""
S.__format__(format_spec) -> str Return a formatted version of S as described by format_spec.
"""
return "" def __getattribute__(self, *args, **kwargs): # real signature unknown
""" Return getattr(self, name). """
pass def __getitem__(self, *args, **kwargs): # real signature unknown
""" Return self[key]. """
pass def __getnewargs__(self, *args, **kwargs): # real signature unknown
pass def __ge__(self, *args, **kwargs): # real signature unknown
""" Return self>=value. """
pass def __gt__(self, *args, **kwargs): # real signature unknown
""" Return self>value. """
pass def __hash__(self, *args, **kwargs): # real signature unknown
""" Return hash(self). """
pass def __init__(self, value='', encoding=None, errors='strict'): # known special case of str.__init__
"""
str(object='') -> str
str(bytes_or_buffer[, encoding[, errors]]) -> str Create a new string object from the given object. If encoding or
errors is specified, then the object must expose a data buffer
that will be decoded using the given encoding and error handler.
Otherwise, returns the result of object.__str__() (if defined)
or repr(object).
encoding defaults to sys.getdefaultencoding().
errors defaults to 'strict'.
# (copied from class doc)
"""
pass def __iter__(self, *args, **kwargs): # real signature unknown
""" Implement iter(self). """
pass def __len__(self, *args, **kwargs): # real signature unknown
""" Return len(self). """
pass def __le__(self, *args, **kwargs): # real signature unknown
""" Return self<=value. """
pass def __lt__(self, *args, **kwargs): # real signature unknown
""" Return self<value. """
pass def __mod__(self, *args, **kwargs): # real signature unknown
""" Return self%value. """
pass def __mul__(self, *args, **kwargs): # real signature unknown
""" Return self*value.n """
pass @staticmethod # known case of __new__
def __new__(*args, **kwargs): # real signature unknown
""" Create and return a new object. See help(type) for accurate signature. """
pass def __ne__(self, *args, **kwargs): # real signature unknown
""" Return self!=value. """
pass def __repr__(self, *args, **kwargs): # real signature unknown
""" Return repr(self). """
pass def __rmod__(self, *args, **kwargs): # real signature unknown
""" Return value%self. """
pass def __rmul__(self, *args, **kwargs): # real signature unknown
""" Return self*value. """
pass def __sizeof__(self): # real signature unknown; restored from __doc__
""" S.__sizeof__() -> size of S in memory, in bytes """
pass def __str__(self, *args, **kwargs): # real signature unknown
""" Return str(self). """
pass 字符串工厂函数 字符串工厂函数
2.2.2.4 常用举例
s.strip()
s.split()
s.find() #搜索，索引或-1
s.index() #搜索，但是报错
s.count()
s.replace()
s.startwith()
s.endwith()
s.isdigit()
s[1:5：2]
# -*-coding:UTF-8-*- # 字符串：
#补充
# x='a' #x=str('a') 字符串操作本质上都是调用str（）
# x.replace ===> str.replace() '''
#字符串类型：引号包含的都是字符串类型
#需要掌握的常用操作： msg='hello'
移除空白 msg.strip()
分割msg.split('|')
长度len(msg)
索引msg[3] msg[-1]
切片msg[0:5:2] #0 2 4
''' # 字符串
# s='hello world'
# s1="hello world"
# s2="""hello world"""
# s3='''hello world'''
# print(type(s))
# print(type(s1))
# print(type(s2))
# print(type(s3)) '''
# x='*****egon********'
# x=x.strip() #strip()方法用于移除字符串头尾指定的字符（默认为空格）。
# print(x)
# print(x.strip('*'))
''' #首字母大写
# x='hello'
# print(x.capitalize()) '''
#所有字母大写
# x='hello'
# print(x.upper())
''' # #居中显示
# x='hello'
# print(x.center(30,'#')) '''
#统计某个字符的长度，空格也算字符
# x='hel lo love'
# print(x.count('l'))
# print(x.count('l',0,4)) # 0 1 2 3
''' # x='hello ' #开始的字符、末尾的字符分别是什么
# print(x.endswith(' '))
# print(x.startswith('h')) '''
# x='hello ' #find() 方法检测字符串中是否包含子字符串 str ，
# print(x.find('e')) #如果指定 beg（开始） 和 end（结束） 范围，则检查是否包含在指定范围内，
# print(x.find('l')) #如果包含子字符串返回开始的索引值，否则返回-1。
''' # 格式化字符串
# msg='Name:{},age:{},sex:{}'
# print(msg) #Name:{},age:{},sex:{}
# print(msg.format('egon',18,'male')) # msg='Name:{0},age:{1},sex:{0}'
# print(msg.format('aaaaaaaaaaaaaaaaa','bbbbbbbbbbbbbb')) # msg='Name:{x},age:{y},sex:{z}'
# print(msg.format(y=18,x='egon',z='male')) '''
# x='hello world'
# print(x[0])
# print(x[4])
# print(x[5])
# print(x[100]) #报错 # print(x[-1])
# print(x[-3])
# print(x[1:3])
# print(x[1:5:2]) #始 末 步长
''' # x='hello' #方法检测字符串中是否包含子字符串 str ，
# print(x.index('o')) #如果指定 beg（开始） 和 end（结束） 范围，则检查是否包含在指定范围内，
# print(x[4]) #该方法与 python find()方法一样，只不过如果str不在 string中会报一个异常。
# print(x[x.index('o')]) '''
# x='123'
# print(x.isdigit()) #检测字符串是否只由数字组成。
#
# age=input('age: ')
# if age.isdigit():
# new_age=int(age)
# print(new_age,type(new_age))
''' # msg='hello alex'
# print(msg.replace('x','X'))
# print(msg.replace('alex','SB'))
# print(msg.replace('l','A'))
# print(msg.replace('l','A',1)) #替换一个
# print(msg.replace('l','A',2)) #替换两个 '''
# x='hello world alex SB'
# x='root:x:0:0::/root:/bin/bash'
# print(x.split(':'))
# split()通过指定分隔符对字符串进行切片，如果参数num 有指定值，则仅分隔 num 个子字符串
# 语法：str.split(str="", num=string.count(str)).
# num是指切几次，切出几个
''' # x='hello'
# # print(x.upper()) #全部变成大写
# x='H'
# print(x.isupper()) #是否是大写
# x='HELLO'
# print(x.islower()) #是否是小写
# print(x.lower()) #全部变成小写 # x=' '
# print(x.isspace()) #是否全是空格 # msg='Hello'
# msg='hEEEE'
# print(msg.istitle()) #首字母大写/字符串中所有的单词拼写首字母是否为大写，且其他字母为小写。
#
# x='hello'
# print(x.title()) #首字母大写 # x='abc'
# print(x.ljust(10,'*'))
# print(x.rjust(10,'*'))
# ljust() 方法返回一个原字符串左对齐,并使用空格填充至指定长度的新字符串。如果指定的长度小于原字符串的长度则返回原字符串。
# 语法：str.ljust(width[, fillchar])
# rjust是右对齐 # x='Ab'
# print(x.swapcase()) #对字符串的大小写字母进行转换。
2.2.3 列表
列表之间可以比较大小，从第一个元素开始比较，只要这个元素能够分出大小就结束
定义：[]内以逗号分隔，按照索引，存放各种数据类型，每个位置代表一个元素
特性：
1.可存放多个值
2.可修改指定索引位置对应的值，可变
3.按照从左到右的顺序定义列表元素，下标从0开始顺序访问，有序
2.2.3.1 列表创建
list_test=[’lhf‘,12,'ok']
或
list_test=list('abc')
或
list_test=list([’lhf‘,12,'ok'])
2.2.3.2 列表常用操作
索引
切片
追加
删除
长度
切片
循环
包含
2.2.4 元组
定义：与列表类似，只不过［］改成（）
特性：
1.可存放多个值
2.不可变
3.按照从左到右的顺序定义元组元素，下标从0开始顺序访问，有序
2.2.4.1 元组创建
ages = (11, 22, 33, 44, 55)
或
ages = tuple((11, 22, 33, 44, 55))
2.2.4.2 元组常用操作
索引
切片
循环
长度
包含
2.2.4.3 元组工厂函数tuple()
2.2.5 字典
定义：｛key1:value1,key2:value2｝,key-value结构，key必须可hash
特性：
1.可存放多个值
2.可修改指定key对应的值，可变
3.无序
2.2.5.1 字典创建
person = {"name": "sb", 'age': 18}
或
person = dict(name='sb', age=18)
person = dict({"name": "sb", 'age': 18})
person = dict((['name','sb'],['age',18]))
{}.fromkeys(seq,100) #不指定100默认为None
注意：
>>> dic={}.fromkeys(['k1','k2'],[])
>>> dic
{'k1': [], 'k2': []}
>>> dic['k1'].append(1)
>>> dic
{'k1': [1], 'k2': [1]}
2.2.5.2 字典常用操作
索引
新增
删除
键、值、键值对
循环
长度
2.2.5.3 字典工厂函数dict()
2.2.6 集合
定义：由不同元素组成的集合，集合中是一组无序排列的可hash值，可以作为字典的key
特性：
1.集合的目的是将不同的值存放到一起，不同的集合间用来做关系运算，无需纠结于集合中单个值
2.2.6.1 集合创建
{1,2,3,1}
或
定义可变集合set
>>> set_test=set('hello')
>>> set_test
{'l', 'o', 'e', 'h'}
改为不可变集合frozenset
>>> f_set_test=frozenset(set_test)
>>> f_set_test
frozenset({'l', 'e', 'h', 'o'})
2.2.6.2 集合常用操作：关系运算
in
not in
＝＝
！＝
<,<=
>,>=
|,|=:合集
&.&=:交集
－,－=:差集
^,^=:对称差分
2.2.7 bytes类型
定义：存8bit整数，数据基于网络传输或内存变量存储到硬盘时需要转成bytes类型,字符串前置b代表为bytes类型
>>> x
'hello sb'
>>> x.encode('gb2312')
b'hello sb'
2.2.8 数据类型转换内置函数汇总
注：真对acsii表unichr在python2.7中比chr的范围更大，python3.*中chr内置了unichar
三 算数运算；逻辑运算；比较运算；关系运算；
四.标准数据类型特性总结
按存值个数区分
| 标量／原子类型 | 数字，字符串 |
| 容器类型 | 列表，元组，字典 |
按可变不可变区分
| 可变 | 列表，字典 |
| 不可变 | 数字，字符串，元组 |
按访问顺序区分
| 直接访问 | 数字 |
| 顺序访问（序列类型） | 字符串，列表，元组 |
| key值访问（映射类型） | 字典 |
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