str字符串

• str
• 转义字符
• 格式化
• 内建函数

字符串

• 表示文字信息
• 用单引号，双引号，三引号引起来

s = 'i love wangxiaojing'
print(s)

i love wangxiaojing

s ="i ch liebe wangxiaojing "
print(s)

i ch liebe wangxiaojing

s ="""
I
love
Xiaojing
"""
print(s)

I
love
Xiaojing

转义字符

• 用一个特色的方法表示出一系列不方便写出的内容，比如回车键，换行符，退格键
• 借助反斜杠字符，一旦字符串中出现反斜杠，则反斜杠后面一个或者几个字符表示已经不是原来
  的意思了，进行了转义
• 在字符串中，一旦出现反斜杠就要加倍小心，可能由转义字符出现
• 不同系统对换行操作有不同表示
  • windows： \n
  • Linux: \r\n

# 转义字符的案例
# 想表达Let's Go
# 使用转义字符
s = 'Let\'s Go'
print(s)# 使用单双引号嵌套
s = "Let's Go"
print(s)# 表示斜杠
# 比如表示C:\User\Augsnao
s = "C:\\user\\Augsnano"
print(s)# 回车换行
# 想表达的效果是：
# lch
# lieb
# wangixaojing
# windows 下也可以使用\r\n,效果相同
s = "lch\rlieb\nWangxiaojing"
print(s)

Let's Go
Let's Go
C:\user\Augsnano
lch
lieb
Wangxiaojing

常用的转义字符

   转义字符   描述\(在行尾时) 续行符    ★\\  反斜杠符号     ★★★\'  单引号       ★★★★★\"  双引号       ★★★★★\a  响铃\b  退格(Backspace)\e  转义\000  空\n  换行         ★★★★★\v  纵向制表符\t  横向制表符     ★★★★★\r  回车         ★★★★★\f  换页\oyy  八进制数，yy代表的字符，例如： \o12代表换行\xyy  十六进制数，yy代表的字符，例如：\x0a代表换行\other 其它的字符以普通的格式输出

# 单个斜杠的用法
# 在python里，单个反斜杠表示此行未结束，处于美观，需要下一行继续
# 理论上应该写成def myDemo(int x, int y, int z):
def myDemo(x,\y,\z):print("hahahhaha")myDemo(1,2,3)

hahahhaha

格式化

• 把字符串按照一定格式进行打印或者填充
• 格式化的分类：
  • 传统格式化
  • format

# 填充
s = "l love wangxiaojing"
print(s)s = "l love lixiajing"
print(s)s = "l love zhangxiaojing"
print(s)

l love wangxiaojing
l love lixiajing
l love zhangxiaojing

字符串的传统格式化方法

• 使用%进行格式化

• %(百分号)也叫占位符

    %s: 字符串%r: 字符串，但是是使用repr而不是str%c: 整数转换为单个字符%d: 十进制整数   %u: 无符号整数 %o: 表示八进制%x: 十六进制，字母为小写(x为小写)%X: 十六进制，字母为大写X为大写)%e: 浮点数(E为小写)，例如2. 87e+12%E: 浮点数(E为大写)，例如2. 87E+12%f,%F: 浮点数十进制形式%g,%G: 十进制形式浮点或者指数浮点自动转换格式字符前出现整数表示此占位符所占位置的宽度格式字符前边出现‘-’ 表示左对齐格式字符前边出现‘+’ 表示右对齐0位数不足用*0'’ 补齐width表示宽度pricision精度
  

# %s 表示简单的字符串
# 占位符可以单独使用
s = "l love %s"
print(s)s = "l love %s"
print(s%"王晓静")#运行到%时检测占位

l love %s
l love 王晓静

print("I love %s"%"李晓静")# %是个占位符，前面是一个字符串，说明%占位符后面必须用字符串
# 占位符一般只能被同类型替换，或者替换类型能被转换成占位符的类型
# 特例
print("I love %s"%100)

I love 李晓静
I love 100

# 占位符是一般只能被同类型替换
s = "yege今年 %d 岁了"
print(s%"十九")  #占位符为十进制整数：%d,所以报错提示需要十进制整数类型，不需要字符串

---------------------------------------------------------------------------TypeError                                 Traceback (most recent call last)<ipython-input-10-c7bcf148ec87> in <module>()1 s = "yege今年 %d 岁了"
----> 2 print(s%"十九")TypeError: %d format: a number is required, not str

s = "I am %f KG weight, %f m Heigh"
print(s)
# 如果需要格式化信息多余一个，则用括号括起来就可以
# 以下打印使用了默认格式，多余打出了好多个零
print(s%(75.3,1.84)) #s中有两个占位符，按顺序替换占位符#实际需要惊醒格式化的信息的数量必须与百分号后面给出的数据数量匹配，否则报错
# 如下例子，实际需要格式化的为4处，但是给出数据为三个，则报错
s = "I am %.2f KG weight, %.2f m Heigh"#.2保留小数点后两位
print(s%(75.3,1.84))

I am %f KG weight, %f m Heigh
I am 75.300000 KG weight, 1.840000 m Heigh
I am 75.30 KG weight, 1.84 m Heigh

format格式化

• 使用函数形式进行格式化，代替以前的百分号

# 不用指定位置，按顺序读取
# 方式1
s = "{} {}!"
print(s.format("Hello","world"))# format中的参数有无限多个# 方式2
s = "{} {}!".format("hello","world")
print(s)# 相当于打印”Hello world”# 设置指定位置
s = "{0} {1}".format("hello","world")
print(s)# 设置指定位置
s = "{1} {0}".format("hello","world")
print(s)# 设置指定位置
s = "I love {0} and {0} loves me".format("hello","world")
print(s)# 下面案例报错，跟上面案列进行对比
#s = "I love {} and {} loves me".format("hello")
#print(s)

Hello world!
hello world!
hello world
world hello
I love hello and hello loves me---------------------------------------------------------------------------IndexError                                Traceback (most recent call last)<ipython-input-40-e80e00c2bede> in <module>()21 22 # 下面案例报错，跟上面案列进行对比
---> 23 s = "I love {} and {} loves me".format("hello")24 print(s)IndexError: tuple index out of range

# 使用命令参数
s = "我们的是{school_name}, 我们的网址是{url}, {teacher}最帅"
s = s.format(school_name="中国科技大学",url="www.baidu.com",teacher="野哥")
print(s)

我们的是中国科技大学, 我们的网址是www.baidu.com, 野哥最帅

# 通过字典设置参数，需要解包
#使用命令参数
s = "我们的是{school_name}, 我们的网址是{url}, {teacher}最帅"s_dict = {"school_name":"中国科技大学",\"url":"www.baidu.com",\"teacher":"yege"}
#**是解包操作
s =s.format(**s_dict)
print(s)

我们的是中国科技大学, 我们的网址是www.baidu.com, yege最帅

# 对数字的格式化需要用到
s = "Liu Dana is {:.2f}m heigh, {:.2f}KG weight"
print(s.format(1.84, 76.45))

Liu Dana is 1.84m heigh, 76.45KG weight^,<,>分别是剧中、左对齐、右对齐，后面带宽度
：号后面带填充的字符，只能是一个字符，不指定则默认是用个空格填充
+ 表示在正数前显示+，负数前显示-， (空格)表示在整数前加空格
d、d、o、x分别是二进制、十进制、八进制、十六进制
此外我们可以使用大括号{}来转义大括号

str内置函数

• 很多语言字符串使用string表示，但是Python中使用str表示字符串

help(str)

Help on class str in module builtins: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'.|  |  Methods defined here:|  |  __add__(self, value, /)|      Return self+value.|  |  __contains__(self, key, /)|      Return key in self.|  |  __eq__(self, value, /)|      Return self==value.|  |  __format__(self, format_spec, /)|      Return a formatted version of the string as described by format_spec.|  |  __ge__(self, value, /)|      Return self>=value.|  |  __getattribute__(self, name, /)|      Return getattr(self, name).|  |  __getitem__(self, key, /)|      Return self[key].|  |  __getnewargs__(...)|  |  __gt__(self, value, /)|      Return self>value.|  |  __hash__(self, /)|      Return hash(self).|  |  __iter__(self, /)|      Implement iter(self).|  |  __le__(self, value, /)|      Return self<=value.|  |  __len__(self, /)|      Return len(self).|  |  __lt__(self, value, /)|      Return self<value.|  |  __mod__(self, value, /)|      Return self%value.|  |  __mul__(self, value, /)|      Return self*value.|  |  __ne__(self, value, /)|      Return self!=value.|  |  __repr__(self, /)|      Return repr(self).|  |  __rmod__(self, value, /)|      Return value%self.|  |  __rmul__(self, value, /)|      Return value*self.|  |  __sizeof__(self, /)|      Return the size of the string in memory, in bytes.|  |  __str__(self, /)|      Return str(self).|  |  capitalize(self, /)|      Return a capitalized version of the string.|      |      More specifically, make the first character have upper case and the rest lower|      case.|  |  casefold(self, /)|      Return a version of the string suitable for caseless comparisons.|  |  center(self, width, fillchar=' ', /)|      Return a centered string of length width.|      |      Padding is done using the specified fill character (default is a space).|  |  count(...)|      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.|  |  encode(self, /, encoding='utf-8', errors='strict')|      Encode the string using the codec registered for encoding.|      |      encoding|        The encoding in which to encode the string.|      errors|        The error handling scheme to use for encoding errors.|        The 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.|  |  endswith(...)|      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.|  |  expandtabs(self, /, tabsize=8)|      Return a copy where all tab characters are expanded using spaces.|      |      If tabsize is not given, a tab size of 8 characters is assumed.|  |  find(...)|      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.|  |  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 '}').|  |  format_map(...)|      S.format_map(mapping) -> str|      |      Return a formatted version of S, using substitutions from mapping.|      The substitutions are identified by braces ('{' and '}').|  |  index(...)|      S.index(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.|      |      Raises ValueError when the substring is not found.|  |  isalnum(self, /)|      Return True if the string is an alpha-numeric string, False otherwise.|      |      A string is alpha-numeric if all characters in the string are alpha-numeric and|      there is at least one character in the string.|  |  isalpha(self, /)|      Return True if the string is an alphabetic string, False otherwise.|      |      A string is alphabetic if all characters in the string are alphabetic and there|      is at least one character in the string.|  |  isascii(self, /)|      Return True if all characters in the string are ASCII, False otherwise.|      |      ASCII characters have code points in the range U+0000-U+007F.|      Empty string is ASCII too.|  |  isdecimal(self, /)|      Return True if the string is a decimal string, False otherwise.|      |      A string is a decimal string if all characters in the string are decimal and|      there is at least one character in the string.|  |  isdigit(self, /)|      Return True if the string is a digit string, False otherwise.|      |      A string is a digit string if all characters in the string are digits and there|      is at least one character in the string.|  |  isidentifier(self, /)|      Return True if the string is a valid Python identifier, False otherwise.|      |      Use keyword.iskeyword() to test for reserved identifiers such as "def" and|      "class".|  |  islower(self, /)|      Return True if the string is a lowercase string, False otherwise.|      |      A string is lowercase if all cased characters in the string are lowercase and|      there is at least one cased character in the string.|  |  isnumeric(self, /)|      Return True if the string is a numeric string, False otherwise.|      |      A string is numeric if all characters in the string are numeric and there is at|      least one character in the string.|  |  isprintable(self, /)|      Return True if the string is printable, False otherwise.|      |      A string is printable if all of its characters are considered printable in|      repr() or if it is empty.|  |  isspace(self, /)|      Return True if the string is a whitespace string, False otherwise.|      |      A string is whitespace if all characters in the string are whitespace and there|      is at least one character in the string.|  |  istitle(self, /)|      Return True if the string is a title-cased string, False otherwise.|      |      In a title-cased string, upper- and title-case characters may only|      follow uncased characters and lowercase characters only cased ones.|  |  isupper(self, /)|      Return True if the string is an uppercase string, False otherwise.|      |      A string is uppercase if all cased characters in the string are uppercase and|      there is at least one cased character in the string.|  |  join(self, iterable, /)|      Concatenate any number of strings.|      |      The string whose method is called is inserted in between each given string.|      The result is returned as a new string.|      |      Example: '.'.join(['ab', 'pq', 'rs']) -> 'ab.pq.rs'|  |  ljust(self, width, fillchar=' ', /)|      Return a left-justified string of length width.|      |      Padding is done using the specified fill character (default is a space).|  |  lower(self, /)|      Return a copy of the string converted to lowercase.|  |  lstrip(self, chars=None, /)|      Return a copy of the string with leading whitespace removed.|      |      If chars is given and not None, remove characters in chars instead.|  |  partition(self, sep, /)|      Partition the string into three parts using the given separator.|      |      This will search for the separator in the string.  If the separator is found,|      returns a 3-tuple containing the part before the separator, the separator|      itself, and the part after it.|      |      If the separator is not found, returns a 3-tuple containing the original string|      and two empty strings.|  |  replace(self, old, new, count=-1, /)|      Return a copy with all occurrences of substring old replaced by new.|      |        count|          Maximum number of occurrences to replace.|          -1 (the default value) means replace all occurrences.|      |      If the optional argument count is given, only the first count occurrences are|      replaced.|  |  rfind(...)|      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.|  |  rindex(...)|      S.rindex(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.|      |      Raises ValueError when the substring is not found.|  |  rjust(self, width, fillchar=' ', /)|      Return a right-justified string of length width.|      |      Padding is done using the specified fill character (default is a space).|  |  rpartition(self, sep, /)|      Partition the string into three parts using the given separator.|      |      This will search for the separator in the string, starting at the end. If|      the separator is found, returns a 3-tuple containing the part before the|      separator, the separator itself, and the part after it.|      |      If the separator is not found, returns a 3-tuple containing two empty strings|      and the original string.|  |  rsplit(self, /, sep=None, maxsplit=-1)|      Return a list of the words in the string, using sep as the delimiter string.|      |        sep|          The delimiter according which to split the string.|          None (the default value) means split according to any whitespace,|          and discard empty strings from the result.|        maxsplit|          Maximum number of splits to do.|          -1 (the default value) means no limit.|      |      Splits are done starting at the end of the string and working to the front.|  |  rstrip(self, chars=None, /)|      Return a copy of the string with trailing whitespace removed.|      |      If chars is given and not None, remove characters in chars instead.|  |  split(self, /, sep=None, maxsplit=-1)|      Return a list of the words in the string, using sep as the delimiter string.|      |      sep|        The delimiter according which to split the string.|        None (the default value) means split according to any whitespace,|        and discard empty strings from the result.|      maxsplit|        Maximum number of splits to do.|        -1 (the default value) means no limit.|  |  splitlines(self, /, keepends=False)|      Return a list of the lines in the string, breaking at line boundaries.|      |      Line breaks are not included in the resulting list unless keepends is given and|      true.|  |  startswith(...)|      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.|  |  strip(self, chars=None, /)|      Return a copy of the string with leading and trailing whitespace remove.|      |      If chars is given and not None, remove characters in chars instead.|  |  swapcase(self, /)|      Convert uppercase characters to lowercase and lowercase characters to uppercase.|  |  title(self, /)|      Return a version of the string where each word is titlecased.|      |      More specifically, words start with uppercased characters and all remaining|      cased characters have lower case.|  |  translate(self, table, /)|      Replace each character in the string using the given translation table.|      |        table|          Translation table, which must be a mapping of Unicode ordinals to|          Unicode ordinals, strings, or None.|      |      The table must implement lookup/indexing via __getitem__, for instance a|      dictionary or list.  If this operation raises LookupError, the character is|      left untouched.  Characters mapped to None are deleted.|  |  upper(self, /)|      Return a copy of the string converted to uppercase.|  |  zfill(self, width, /)|      Pad a numeric string with zeros on the left, to fill a field of the given width.|      |      The string is never truncated.|  |  ----------------------------------------------------------------------|  Static methods defined here:|  |  __new__(*args, **kwargs) from builtins.type|      Create and return a new object.  See help(type) for accurate signature.|  |  maketrans(x, y=None, z=None, /)|      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.

Python str 模块相关推荐

1. python str模块

   str字符串 str 转义字符 格式化 内建函数 字符串 表示文字信息 用单引号,双引号,三引号括起来 s = 'I love ' print(s) 复制代码 I love 复制代码 s = &quo ...

2. Python中的文本处理（一）str 模块完全解析

   前言 字符串处理是编程中常用到的操作,本系列总结的目标是通过系统的介绍不同的方法来完成不同复杂度的字符串处理操作. 旨在方便大家遇到不同的需求时,可以快速找到合适的处理方式,从而使代码开发快速,简洁, ...

3. python io模块_python中的StringIO模块

   原博文 2015-10-23 15:21 − # python中的StringIO模块 标签:python StringIO --- > 此模块主要用于在内存缓冲区中读写数据.模块是用类编写的, ...

4. 实战篇一 python常用模块和库介绍

   # -_-@ coding: utf-8 -_-@ -- Python 常用模块和库介绍 第一部分:json模块介绍 import json 将一个Python数据结构转换为JSON: dict_ = ...

5. 对于python来说、一个模块就是一个文件-python常用模块

   python常用模块 什么是模块? 常见的场景:一个模块就是一个包含了python定义和声明的文件,文件名就是模块名字加上.py的后缀. 但其实import加载的模块分为四个通用类别: 1 使用pyt ...

6. python email模块

   python email模块 官方文档 email模块 电子邮件包是一个用于管理电子邮件消息的库.它的特殊设计不用于向SMTP (RFC 2821).NNTP或其他服务器发送任何电子邮件消息;这些是模 ...

7. Day05 - Python 常用模块

   1. 模块简介 模块就是一个保存了 Python 代码的文件.模块能定义函数,类和变量.模块里也能包含可执行的代码. 模块也是 Python 对象,具有随机的名字属性用来绑定或引用. 下例是个简单的模 ...

8. python str输出到txt_Python 速学！不懂怎么入门python的小白看这篇就够了！

   Python是一种非常流行的脚本语言,而且功能非常强大,几乎可以做任何事情,比如爬虫.网络工具.科学计算.树莓派.Web开发.游戏等各方面都可以派上用场.同时无论在哪种平台上,都可以用 Python ...

9. 「学习笔记——Python」Python 的模块(Modules)

   6 Python的模块 (Modules) Table of Contents 1 关于模块 1.1 更多关于模块的故事 1.2 将模块作为脚体执行 1.3 模块搜索路径 1.4 "编译过的 ...

10. 【Python基础】Python时间模块，超实用总结！

    我的施工之路 施工之路已完成13篇图文,又提炼为思维导图,结合使用,效果最佳. 1我的施工计划 2数字专题 3字符串专题 4列表专题 5流程控制专题 6编程风格专题 7函数使用 8面向对象编程(上篇) ...

最新文章

1. 《移动数据挖掘》—— 第1章 引言 1.1 移动数据及其价值
2. 数格子算面积的方法_水基材料防锈试验方法：铸铁粉末法
3. K8s 集群节点在线率达到 99.9% 以上，扩容效率提升 50%，我们做了这 3 个深度改造
4. 【通知】如何让你的2020年秋招CV项目经历更加硬核，可深入学习有三秋季划4大领域32个方向...
5. 一、linux的安装
6. Python【每日一问】16
7. P3435 [POI2006]OKR-Periods of Words kmp + fail指针
8. LINUX下载编译vo-amrwbenc
9. vivado修改下载器下载速率
10. srs流媒体服务器拉流的流程
11. 如何用范德蒙行列式完成插值
12. 如何在 Mac 上更改文件夹颜色，改变 mac 文件夹颜色教程
13. python cad按范围裁剪
14. SnakeGame(贪吃蛇游戏)
15. 带参数矩阵求逆（matlab)
16. TZT3801G无线振弦在线监测系统
17. [NSSCTF][SCTF 2021]WEB复现
18. echarts-箱线图(盒须图)
19. 三星s5 安装android,三星手机怎么安装软件？三星手机安装被阻止情况的解决办法介绍...
20. 使用STM32CUBEMX HAL库读写SD卡

热门文章

1. u盘启动计算机的几种方式,U盘各种启动模式方法介绍 六种U盘启动模式
2. 大数据可视化技术：可视化技术概述与Echarts入门
3. 比特客区块链 | 从A到Z速记区块链词汇表
4. 哪些命令可以关闭计算机 poweroff,虚拟机常用命令
5. vue4 跳转外部链接_vue项目跳转到外部链接
6. 网卡超时实现机制 watchdog_timeo／ndo_tx_timeout
7. 如何解决python中文问题_布同：如何解决Python中文问题（总结了多位前人经验，初学者必看）...
8. 6.Cython使用WinGw编译pyd
9. linux常用桌面有两种,推荐！5款Linux常用桌面环境
10. oracle函数按周,关于oracle按日周月分组统计以及next_day()函数详解