总结Python数据类型及其方法

Python数据类型及其方法详解

我们在学习编程语言的时候，都会遇到数据类型，这种看着很基础也不显眼的东西，却是很重要，本文介绍了python的数据类型，并就每种数据类型的方法作出了详细的描述，可供知识回顾。

一、整型和长整型

整型：数据是不包含小数部分的数值型数据，比如我们所说的1、2、3、4、122，其type为"int"长整型：也是一种数字型数据，但是一般数字很大，其type为"long"在python2中区分整型和长整型，在32位的机器上，取值范围是-2147483648~2147483647,超出范围的为长整型，在64位的机器上，取值范围为-9223372036854775808～9223372036854775807（通常也与python的解释器的位数有关）。在python3中，不存在整型和长整型之分，只有整型。举个例子：

python2中
number = 123print (type(number))
number2 = 2147483647print (type(number2))
number2 = 2147483648 #我们会看到超过2147483647这个范围，在py2中整形就会变成长整形了print (type(number2))#运行结果<type 'int'>
<type 'int'>
<type 'long'>#python3中number = 123print (type(number))
number2 = 2147483648 
print (type(number2)) #在python3中并不会#运行结果<class 'int'>
<class 'int'>

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常用的method的如下：

.bit_length()

取最短bit位数

 def bit_length(self): # real signature unknown; restored from __doc__"""int.bit_length() -> int
 
 Number of bits necessary to represent self in binary.
 >>> bin(37)
 '0b100101'
 >>> (37).bit_length()
 6"""return 0

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举个例子：

number = 12 #1100 print(number.bit_length())#运行结果4

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二、浮点型

浮点型可以看成就是小数，type为float。

#浮点型number = 1.1print(type(number))#运行结果<class 'float'>

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常用method的如下：

.as_integer_ratio()

返回元组(X,Y)，number = k ,number.as_integer_ratio() ==>（x,y） x/y=k

 def as_integer_ratio(self): # real signature unknown; restored from __doc__"""float.as_integer_ratio() -> (int, int)
 
 Return a pair of integers, whose ratio is exactly equal to the original
 float and with a positive denominator.
 Raise OverflowError on infinities and a ValueError on NaNs.
 
 >>> (10.0).as_integer_ratio()
 (10, 1)
 >>> (0.0).as_integer_ratio()
 (0, 1)
 >>> (-.25).as_integer_ratio()
 (-1, 4)"""pass

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举个例子

number = 0.25print(number.as_integer_ratio())#运行结果(1, 4)

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.hex()

以十六进制表示浮点数

 def hex(self): # real signature unknown; restored from __doc__"""float.hex() -> string
 
 Return a hexadecimal representation of a floating-point number.
 >>> (-0.1).hex()
 '-0x1.999999999999ap-4'
 >>> 3.14159.hex()
 '0x1.921f9f01b866ep+1'"""return ""

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举个例子

number = 3.1415print(number.hex())#运行结果0x1.921cac083126fp+1

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.fromhex（）

将十六进制小数以字符串输入，返回十进制小数

 def fromhex(string): # real signature unknown; restored from __doc__"""float.fromhex(string) -> float
 
 Create a floating-point number from a hexadecimal string.
 >>> float.fromhex('0x1.ffffp10')
 2047.984375
 >>> float.fromhex('-0x1p-1074')
 -5e-324"""

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举个例子

print(float.fromhex('0x1.921cac083126fp+1'))#运行结果3.1415

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.is_integer()

判断小数是不是整数，比如3.0为一个整数，而3.1不是，返回布尔值

 def is_integer(self, *args, **kwargs): # real signature unknown""" Return True if the float is an integer. """pass

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举个例子

number = 3.1415number2 = 3.0print(number.is_integer())print(number2.is_integer())#运行结果False
True

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三、字符类型

字符串就是一些列的字符，在Python中用单引号或者双引号括起来，多行可以用三引号。

name = 'my name is Frank'name1 = "my name is Frank"name2 = '''my name is Frank
I'm 23 years old, 
 '''print(name)print(name1)print(name2)#运行结果my name is Frank
my name is Frank
my name is Frank
I'm 23 years old

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常用method的如下：

.capitalize()

字符串首字符大写

 def capitalize(self): # real signature unknown; restored from __doc__"""S.capitalize() -> str
 
 Return a capitalized version of S, i.e. make the first character
 have upper case and the rest lower case."""return ""

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举个例子

name = 'my name is Frank'#运行结果My name is frank

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.center()

字符居中，指定宽度和填充字符（默认为空格）

 def center(self, width, fillchar=None): # real signature unknown; restored from __doc__"""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 ""

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举个例子

flag = "Welcome Frank"print(flag.center(50,'*'))#运行结果******************Welcome Frank*******************

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.count()

计算字符串中某个字符的个数，可以指定索引范围

 def count(self, sub, start=None, end=None): # real signature unknown; restored from __doc__"""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

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举个例子

flag = 'aaababbcccaddadaddd'print(flag.count('a'))print(flag.count('a',0,3))#运行结果7
3

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.encode()

编码，在python3中，str默认是unicode数据类型，可以将其编码成bytes数据

 def encode(self, encoding='utf-8', errors='strict'): # real signature unknown; restored from __doc__"""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""

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举个例子

flag = 'aaababbcccaddadaddd'print(flag.encode('utf8'))#运行结果b'aaababbcccaddadaddd'

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.endswith()

判断字符串结尾是否是某个字符串和字符，可以通过索引指定范围

 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

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举个例子

flag = 'aaababbcccaddadaddd'print(flag.endswith('aa'))print(flag.endswith('ddd'))print(flag.endswith('dddd'))print(flag.endswith('aaa',0,3))print(flag.endswith('aaa',0,2))#运行结果False
True
False
True
False

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.expandtabs()

把制表符tab(" ")转换为空格

 def expandtabs(self, tabsize=8): # real signature unknown; restored from __doc__"""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 ""

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举个例子

flag = "	hello python!"print(flag)print(flag.expandtabs()) #默认tabsize=8print(flag.expandtabs(20))#运行结果hello python! #一个tab，长度为4个空格hello python! #8个空格hello python! #20个空格

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.find()

查找字符，返回索引值，可以通过指定索引范围内查找，查找不到返回-1

 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

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举个例子

flag = "hello python!"print(flag.find('e'))print(flag.find('a'))print(flag.find('h',4,-1))#运行结果1
-1
9

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.format()

格式化输出，使用"{}"符号作为操作符。

def format(self, *args, **kwargs): # known special case of str.format"""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

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举个例子

#位置参数flag = "hello {0} and {1}!"print(flag.format('python','php'))
flag = "hello {} and {}!"print(flag.format('python','php'))#变量参数flag = "{name} is {age} years old!"print(flag.format(name='Frank',age = 23))#结合列表infor=["Frank",23]print("{0[0]} is {0[1]} years old".format(infor))#运行结果hello python and php!
hello python and php!
Frank is 23 years old!
Frank is 23 years old

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.format_map()

格式化输出

 def format_map(self, mapping): # real signature unknown; restored from __doc__"""S.format_map(mapping) -> str
 
 Return a formatted version of S, using substitutions from mapping.
 The substitutions are identified by braces ('{' and '}')."""return ""

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举个例子

people={'name':['Frank','Caroline'],'age':['23','22'],
}print("My name is {name[0]},i am {age[1]} years old !".format_map(people))#运行结果My name is Frank,i am 22 years old !

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.index()

根据字符查找索引值，可以指定索引范围查找，查找不到会报错

 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

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举个例子

flag = "hello python!"print(flag.index("e"))print(flag.index("o",6,-1))#运行结果1
10

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.isalnum()

判断是否是字母或数字组合，返回布尔值

def isalnum(self): # real signature unknown; restored from __doc__"""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

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举个例子

flag = "hellopython"flag1 = "hellopython22"flag2 = "hellopython!!"flag3 = "!@#!#@!!@"print(flag.isalnum())print(flag1.isalnum())print(flag2.isalnum())print(flag3.isalnum())#运行结果True
True
False
False

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.isalpha()

判断是否是字母组合，返回布尔值

 def isalpha(self): # real signature unknown; restored from __doc__"""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

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举个例子

flag = "hellopython"flag1 = "hellopython22"print(flag.isalpha())print(flag1.isalpha())#运行结果True
False

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.isdecimal()

判断是否是一个十进制正整数，返回布尔值

 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

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举个例子

number = "1.2"number1 = "12"number2 = "-12"number3 = "1222"print(number.isdecimal())print(number1.isdecimal())print(number2.isdecimal())print(number3.isdecimal())#运行结果False
True
False
True

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isdigit()

判断是否是一个正整数，返回布尔值，与上面isdecimal类似

 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

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举个例子

number = "1.2"number1 = "12"number2 = "-12"number3 = "11"print(number.isdigit())print(number1.isdigit())print(number2.isdigit())print(number3.isdigit())#运行结果False
True
False
True

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.isidentifier()

判断是否为python中的标识符

 def isidentifier(self): # real signature unknown; restored from __doc__"""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

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举个例子

flag = "cisco"flag1 = "1cisco"flag2 = "print"print(flag.isidentifier())print(flag1.isidentifier())print(flag2.isidentifier())#运行结果True
False
True

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.islower()

判断字符串中的字母是不是都是小写，返回布尔值

 def islower(self): # real signature unknown; restored from __doc__"""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

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举个例子

flag = "cisco"flag1 = "cisco222"flag2 = "Cisco"print(flag.islower())print(flag1.islower())print(flag2.islower())#运行结果True
True
False

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.isnumeric()

判断是否为数字，这个很强大，中文字符，繁体字数字都可以识别

 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

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举个例子

number = "123"number1 = "一"number2 = "壹"number3 = "123q"number4 = "1.1"print(number.isnumeric())print(number1.isnumeric())print(number2.isnumeric())print(number3.isnumeric())print(number4.isnumeric())#运行结果True
True
True
False
False

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.isprintable()

判断引号里面的是否都是可打印的，返回布尔值

 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

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举个例子

flag = "
123"flag1 = "	"flag2 = "123"flag3 = r"
123" # r 可以是转义字符失效print(flag.isprintable()) #
不可打印print(flag1.isprintable()) #	不可打印print(flag2.isprintable())print(flag3.isprintable())#运行结果False
False
True
True

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.isspace()

判断字符串里面都是空白位，空格或者tab，返回布尔值

 def isspace(self): # real signature unknown; restored from __doc__"""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

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举个例子

flag = ' ' #4个空格flag1 = ' '#2个tabprint(flag.isspace())print(flag1.isspace())#运行结果True
True

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.istitle()

判断字符串里面的字符是否都是大写开头，返回布尔值

 def isspace(self): # real signature unknown; restored from __doc__"""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

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举个例子

flag = "Welcome Frank"flag1 = "Welcome frank"print(flag.istitle())print(flag1.istitle())#运行结果True
False

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.isupper()

判断是否都是字符串里的字母都是大写

 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

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举个例子

flag = "WELCOME1"flag1 = "Welcome1"print(flag.isupper())print(flag1.isupper())#运行结果True
False

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.join()

将字符串以指定的字符连接生成一个新的字符串

 def join(self, iterable): # real signature unknown; restored from __doc__"""S.join(iterable) -> str
 
 Return a string which is the concatenation of the strings in the
 iterable. The separator between elements is S."""return ""

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举个例子

flag = "welcome"print("#".join(flag))#运行结果w#e#l#c#o#m#e

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.ljust()

左对齐，可指定字符宽度和填充字符

 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 ""

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举个例子

flag = "welcome"print(flag.ljust(20,"*"))#运行结果welcome*************

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.rjust()

右对齐，可指定字符宽度和填充字符

 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 ""

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举个例子

flag = "welcome"print(flag.rjust(20,"*"))#运行结果*************welcome

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.lower()

对字符串里的所有字母转小写

 def lower(self): # real signature unknown; restored from __doc__"""S.lower() -> str
 
 Return a copy of the string S converted to lowercase."""return ""

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举个例子

flag = "WELcome"#运行结果welcome

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.upper()

对字符串里的所有字母转大写

 def upper(self): # real signature unknown; restored from __doc__"""S.upper() -> str
 
 Return a copy of S converted to uppercase."""return ""

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举个例子

flag = "WELcome"print(flag.upper())#运行结果WELCOME

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.title()

对字符串里的单词进行首字母大写转换

 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 ""

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举个例子

flag = "welcome frank"print(flag.title())#运行结果Welcome Frank

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.lstrip()

默认去除左边空白字符，可指定去除的字符，去除指定的字符后，会被空白占位。

 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 ""

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举个例子

flag = " welcome frank"flag1 = "@@@@welcome frank"print(flag.lstrip())print(flag.lstrip("@"))print(flag.lstrip("@").lstrip())#运行结果welcome frank
 welcome frank
welcome frank

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.rstrip()

默认去除右边空白字符，可指定去除的字符，去除指定的字符后，会被空白占位。

 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 ""

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举个例子

flag = "welcome frank "flag1 = "welcome frank@@@@"# print(flag.title())print(flag.rstrip())print(flag.rstrip("@"))print(flag.rstrip("@").rstrip())#运行结果welcome frank
welcome frank #右边有4个空格welcome frank

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.strip()

默认去除两边空白字符，可指定去除的字符，去除指定的字符后，会被空白占位。

 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 ""

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举个例子

flag = " welcome frank "flag1 = "@@@@welcome frank@@@@"# print(flag.title())print(flag.strip())print(flag.strip("@"))print(flag.strip("@").strip())#运行结果welcome frank
 welcome frank #右边有4个空格welcome frank

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.maketrans()和translate()

创建字符映射的转换表，对于接受两个参数的最简单的调用方式，第一个参数是字符串，表示需要转换的字符，第二个参数也是字符串表示转换的目标。两个字符串的长度必须相同，为一一对应的关系。

 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

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 def translate(self, table): # real signature unknown; restored from __doc__"""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 ""

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举个例子

intab = "aeiou"outtab = "12345"trantab = str.maketrans(intab, outtab)
str = "this is string example....wow!!!"print (str.translate(trantab))#运行结果th3s 3s str3ng 2x1mpl2....w4w!!!

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.partition()

以指定字符分割，返回一个元组