Python基础知识：字符串
1、Python中大写字母命名的变量，默认为常量，不可修改；列如：MYSQL_CONNECTION = '192.168.1.1'
2、字符串换行输入格式：换行用\隔开，两行分别用引号，制表符\t,换行符\n
famous_person = "Albert Einstein"
message = famous_person+"once said,A person who never \n\t"\
"made a mistake never tried anything new."
print(message)
3、type() 查看数据类型
#int整型 a=0 print(type(a)) #str字符串 b='charlie' print(type(b)) #float浮点型 c=1.5 print(type(c))
4、布尔值：真或假 o==False 1==True
5、字符串基本操作
name = " char Lie,Alex "
print(' ' in name) #判断有没有空格
print(name.title())#首字母大写
print(name.upper())#全部变为大写
print(name.lower())#全部变为小写
print(name.rstrip())#删除末尾空白
print(name.lstrip())#删除开头空白
print(name.strip())#删除两端空白
print(name.replace(' ',''))#删除所有空白
6、split(),join(),字符串的分割与合并
name = 'alex,alice,james' name2 = name.split(',')#字符串以逗号分割，变为列表 print(name2) print('|'.join(name2))#将列表中的字符串以|合并为字符串
7、调用re模块，删除字符串中的特殊字符和空格
#删除特殊符号和空格 import re s = 'charlie $ # % * & daifu' print(re.sub('[$\#\%\*\&\ ]','',s))
8、格式化输出：%s-字符串，%d-整型，%f-浮点型
''' 字符格式化输出: %s 输出字符串 %d 输出十进制整数 %f 输出浮点型数据（包括单双精度），以小数形式输出 ''' #2代表保留两位小数，四舍五入 s = "%.2f"%1.256 print(s) #字符串中有%，需要两个%才能输出 s = "charlie %s %%3"%('is') print(s)
#charlie is %3
#常用的字符串格式化功能 tpl = "i am %s" % "alex" tpl = "i am %s age %d" % ("alex", 18) tpl = "i am %(name)s age %(age)d" % {"name": "alex", "age": 18} tpl = "percent %.2f" % 99.97623 tpl = "i am %(pp).2f" % {"pp": 123.425556, } tpl = "i am %% %(pp).2f " % {"pp": 123.425556, } #i am % 123.43
name=input("input your name:") age=input("input your age:") job=input("input your job:") #多行字符串用两个三引号框起来 msg=''' information of user %s: ------------------- name: %s age : %s job : %s --------End-------- '''%(name,name,age,job) print(msg)
9、format()字符格式化，变量存储在字典中
msg = 'Hello {name},it is {number} years no see.' #使用**kwargs传递参数 msg1 = msg.format(name='alex',number=10) print(msg1) msg2 = msg.format(**｛name='alex',number=10｝) print(msg2) #使用*args传递参数 msg = 'hello {0},{1} years no see.' msg1 = msg.format('alex',10) print(msg1) msg2= msg.format(*['alex',10]) print(msg2)
#format()常用格式化 tpl = "i am {}, age {}, {}".format("seven", 18, 'alex') tpl = "i am {}, age {}, {}".format(*["seven", 18, 'alex']) tpl = "i am {0}, age {1}, really {0}".format("seven", 18) tpl = "i am {0}, age {1}, really {0}".format(*["seven", 18]) tpl = "i am {name}, age {age}, really {name}".format(name="seven", age=18) tpl = "i am {name}, age {age}, really {name}".format(**{"name": "seven", "age": 18}) tpl = "i am {0[0]}, age {0[1]}, really {0[2]}".format([1, 2, 3], [11, 22, 33]) tpl = "i am {:s}, age {:d}, money {:f}".format("seven", 18, 88888.1) tpl = "i am {:s}, age {:d}".format(*["seven", 18]) tpl = "i am {name:s}, age {age:d}".format(name="seven", age=18) tpl = "i am {name:s}, age {age:d}".format(**{"name": "seven", "age": 18}) tpl = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2) tpl = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2) tpl = "numbers: {0:b},{0:o},{0:d},{0:x},{0:X}, {0:%}".format(15) tpl = "numbers: {num:b},{num:o},{num:d},{num:x},{num:X}, {num:%}".format(num=15)
10、center() 字符串在中间不满长度的用-填充
name = 'Lebran James' print(name.center(40,'-'))
11、find() 检查字符串是否存在，如果存在返回索引，不存在则返回-1
name = 'Lebran James' print(name.find('a')) print(name.find('g'))
12、isalnum()检查字符串是否包含特殊字符（除了字母和数字，空格也算特殊）
endswith('ab')检查以什么字符结尾
startswith('Le')检查以什么字符开始
isdigit()检查字符串是否为纯数字
name = 'Lebran James' print(name.isalnum())#检查是否包含特殊字符（除了字母和数字，空格也算特殊） print(name.endswith('es'))#检查以什么字符结尾 print(name.startswith('Le'))#以什么字符开始 number = '122' print(number.isdigit())#检查字符串是否为纯数字
13、capitalize()字符串的第一个字母大写
#字符串的第一个字母大写 name = 'lebran james' name = name.capitalize() print(name)
