一、字符串的创建
test = str() / ""
test = str("licheng") / "licheng"
- 无参数，创建空字符串
- 一个参数，创建普通字符串
- 两个参数，int（字节，编码）
二、字符串的常用方法
#capitalize()：字符串首字符大写
string = ‘this is a string.‘
new_str = string.capitalize()
print(new_str)
#输出：This is a string.
#center(width, fillchar=None)：将字符串放在中间，在指定长度下，首尾以指定字符填充
string = ‘this is a string.‘
new_str = string.center(30,‘*‘)
print(new_str)
#输出：******this is a string.*******
#count(sub, start=None, end=None)：计算字符串中某字符的数量
string = ‘this is a string.‘
new_str = string.count(‘i‘)
print(new_str)
#输出：3
#decode/encode(encoding=None, errors=None)：解码/解码
string = ‘this is a string.‘
new_str = string.decode()
new_str = string.encode()
print(new_str)
#endswith(self, suffix, start=None, end=None)：判断是否以某字符结尾
string = ‘this is a string.‘
new_str = string.endswith(‘ing.‘)
print(new_str)
#输出：True
#find(self, sub, start=None, end=None)：在字符串中寻找指定字符的位置
string = ‘this is a string.‘
new_str = string.find(‘a‘) #找的到的情况
print(new_str)
#输出：8
new_str = string.find(‘xx‘) #找不到的情况返回-1
print(new_str)
#输出：-1
#index(self, sub, start=None, end=None)：；类似find
string = ‘this is a string.‘
new_str = string.index(‘a‘) #找的到的情况
print(new_str)
#输出：8
new_str = string.index(‘xx‘) #找不到的情况，程序报错
print(new_str)
#输出：程序运行报错，ValueError: substring not found
#isalnum(self)：判断字符串中是否都是数字和字母，如果是则返回True，否则返回False
string = ‘My name is yue,my age is 18.‘
new_str = string.isalnum()
print(new_str)
#输出：False
string = ‘haha18121314lala‘
new_str = string.isalnum()
print(new_str)
#输出：True
#isalpha(self)：判断字符串中是否都是字母，如果是则返回True，否则返回False
string = ‘abcdefg‘
new_str = string.isalpha()
print(new_str)
#输出：True
string = ‘my name is yue‘
new_str = string.isalpha() #字母中间带空格、特殊字符都不行
print(new_str)
#输出：False
# isdigit(self)：判断字符串中是否都是数字，如果是则返回True，否则返回False
string = ‘1234567890‘
new_str = string.isdigit()
print(new_str)
#输出：True
string = ‘haha123lala‘
new_str = string.isdigit() #中间带空格、特殊字符都不行
print(new_str)
#输出：False
# islower(self)：判断字符串中的字母是否都是小写，如果是则返回True，否则返回False
string = ‘my name is yue,my age is 18.‘
new_str = string.islower()
print(new_str)
#输出：True
string = ‘My name is Yue,my age is 18.‘
new_str = string.islower()
print(new_str)
#输出：False
# isupper(self)：检测字符串中所有的字母是否都为大写。
string = ‘MY NAME IS YUE.‘
new_str = string.isupper()
print(new_str)
#输出：True
string = ‘My name is Yue.‘
new_str = string.isupper()
print(new_str)
#输出：False
# join(self, iterable)：将序列中的元素以指定的字符连接生成一个新的字符串。
string = ("haha","lala","ohoh")
str = "-"
print(str.join(string))
#输出：haha-lala-ohoh
# lower(self)：转换字符串中所有大写字符为小写。
string = "My Name is YUE."
print(string.lower())
# 输出：my name is yue.
# lstrip(self, chars=None)：截掉字符串左边的空格或指定字符。
string = " My Name is YUE."
print(string.lstrip())
#输出：My Name is YUE.
string = "My Name is YUE."
print(string.lstrip(‘My‘))
#输出： Name is YUE.
#replace(self, old, new, count=None)：把字符串中的 old（旧字符串） 替换成 new(新字符串)，如果指定第三个参数max，则替换不超过 max 次。
string = "My name is yue."
print(string.replace("yue","ying"))
#输出：My name is ying.
# rfind(self, sub, start=None, end=None)：返回字符串最后一次出现的位置，如果没有匹配项则返回-1。
string = "My name is yue."
print(string.rfind(‘is‘))
#输出：8
string = "My name is yue."
print(string.rfind(‘XXX‘))
#输出：-1
# split(self, sep=None, maxsplit=None)：通过指定分隔符对字符串进行切片。
string = "haha lala gege"
print(string.split(‘ ‘))
#输出：[‘haha‘, ‘lala‘, ‘gege‘]
print(string.split(‘ ‘, 1 ))
#输出： [‘haha‘, ‘lala gege‘]
# rsplit(self, sep=None, maxsplit=None)：通过指定分隔符对字符串从右进行切片。
string = "haha lala gege"
print(string.rsplit(‘ ‘))
#输出：[‘haha‘, ‘lala‘, ‘gege‘]
print(string.rsplit(‘ ‘, 1 ))
#输出： [‘haha lala‘, ‘gege‘]
# rstrip(self, chars=None)：删除 string 字符串末尾的指定字符（默认为空格）.
string = " My name is yue. "
print(string.rstrip())
#输出： My name is yue.
# strip(self, chars=None)：移除字符串头尾指定的字符（默认为空格）。
string = " My name is yue. "
print(string.strip())
#输出：My name is yue.
# upper(self)：将字符串中的小写字母转为大写字母。
string = "my name is yue,my age is 18."
print(string.upper())
#输出：MY NAME IS YUE,MY AGE IS 18.
str源码
三、字符串的公共功能
- 索引（只能取一个元素）
- 切片（取多个元素）
- 长度（len）
- python2：按字节算长度
- python3：按字符算长度
- for循环（同长度的版本循环单位）
四、字符与字节的转换
# 将gbk编码的字符转化为字节 s = "李程" b = bytes(s, encoding="gbk") type(b) 输出为字节类型 # 将字节转化为字符 c = str(b, encoding="gbk")
五、字符串格式化
Python的字符串格式化有两种方式: 百分号方式、format方式
百分号的方式相对来说比较老，而format方式则是比较先进的方式，企图替换古老的方式，目前两者并存。
1、百分号方式
%[(name)][flags][width].[precision]typecode
参数详解
常用格式化：
tpl = "i am %s" % "spark"
tpl = "i am %s age %d" % ("spark", 18)
tpl = "i am %(name)s age %(age)d" % {"name": "spark", "age": 18}
tpl = "percent %.2f" % 99.97623
tpl = "i am %(pp).2f" % {"pp": 123.425556, }
tpl = "i am %.2f %%" % {"pp": 123.425556, }
2、Format方式
[[fill]align][sign][#][0][width][,][.precision][type]
参数详解
常用格式化：
1 tpl = "i am {}, age {}, {}".format("seven", 18, ‘alex‘)
2
3 tpl = "i am {}, age {}, {}".format(*["seven", 18, ‘alex‘])
4
5 tpl = "i am {0}, age {1}, really {0}".format("seven", 18)
6
7 tpl = "i am {0}, age {1}, really {0}".format(*["seven", 18])
8
9 tpl = "i am {name}, age {age}, really {name}".format(name="seven", age=18)
10
11 tpl = "i am {name}, age {age}, really {name}".format(**{"name": "seven", "age": 18})
12
13 tpl = "i am {0[0]}, age {0[1]}, really {0[2]}".format([1, 2, 3], [11, 22, 33])
14
15 tpl = "i am {:s}, age {:d}, money {:f}".format("seven", 18, 88888.1)
16
17 tpl = "i am {:s}, age {:d}".format(*["seven", 18])
18
19 tpl = "i am {name:s}, age {age:d}".format(name="seven", age=18)
20
21 tpl = "i am {name:s}, age {age:d}".format(**{"name": "seven", "age": 18})
22
23 tpl = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2)
24
25 tpl = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2)
26
27 tpl = "numbers: {0:b},{0:o},{0:d},{0:x},{0:X}, {0:%}".format(15)
28
29 tpl = "numbers: {num:b},{num:o},{num:d},{num:x},{num:X}, {num:%}".format(num=15)
更多格式化操作：https://docs.python.org/3/library/string.html
时间： 2024-10-13 19:34:17