phthon字符与list常用方法和属性

字符

methods :

1. count:统计字符在字符串中出现的次数（return　int）

[searchStr,startIndex,endIndex]

mypty = 'This is a demo of the count method of str'
print(mypty.count('i', 0, len(mypty))) # 2
# 找不到则返回０
print(mypty.count('z', 0, len(mypty)))  # ０

2. find 在字符串里找到第一个符合查找条件的字符的下标（return　int）　

[searchStr,startIndex,endIndex]

mypty = 'This is a demo of the find method of str'　　　　
print(mypty.find('i', 0, len(mypty))) # 2　　
# 找不到则返回-1
print(mypty.find('z', 0, len(mypty)))  # -1

3. replace 在字符串中替换指定的字符 (return new str)

[beforeStr,afterStr,replaceCount] replaceCount:默认全部替换

mypty = 'This is a demo of the replace method of str'
newMypty = mypty.replace('is', 'are')
print(newMypty) # Thare are a demo of the replace method of str

4. upper & isupper ： 将字符转换为全大写 & 字符内是否都是大写

upper : (return upper str)
isupper : return Boolean

mypty = 'this is a demo of the upper method of str'
print(mypty.upper()) # THIS IS A DEMO OF THE UPPER METHOD OF STR
newMypty = mypty.upper()
print(newMypty.isupper()) # True

5. lower & islower ： 将字符转换为全小写 & 字符内是否都是小写

lower : (return lower str)
islower : return Boolean

mypty = 'THIS IS A DEMO OF THE LOWER METHOD OF STR'  
print(mypty.lower()) # this is a demo of the lower method of str
newMypty = mypty.lower()
print(newMypty.islower()) # True

6. split : 将字符基于指定字符分割成一个list,没有参数则默认以空格为分割符

Return a list of the words in the string, using sep as the delimiter string.

[splitKey,splitCount]
return list

mypty = 'this is a demo of the split method of str'
print(mypty.split(' ')) # 基于空格分割 ['this', 'is', 'a', 'demo', 'of', 'the', 'split', 'method', 'of', 'str']

7. strip : 去除一个字符前后两边的指定字符，不传参则去除两边空格（一侧有也可以替换，不穿参数则只能替换两侧空格）

如果想要替换中间的空格符，则可以使用str.replace(' ','')实现

Return a copy of the string with leading and trailing whitespace removed. If chars is given and not None, remove characters in chars instead.

return stripped str

# 没有参数
mypty = '   this is a demo of the split method of str    '
print(mypty ) # '   this is a demo of the split method of str    ' # 初始有两边空格
print(mypty.strip()) # 'this is a demo of the split method of str' 无两边空格

#有参数
mypty = 'zzzthis is a demo of the split method of strzzz'
print(mypty) # 'zzzthis is a demo of the split method of strzzz'
print(mypty.strip('zzz')) # 'this is a demo of the split method of str'

#错误参数，则返回原字符
print(mypty.strip('sss')) # 'zzzthis is a demo of the split method of strzzz'

8.格式化输出

1. %s

语法：str%s%{value} 其中s指占位符 ，后面的百分比后的大括号标识s对应的值

允许为数字、字符、字l典、list类型

demostr = '致%s'%('爱丽丝')
print(demostr) # 致爱丽丝
demostr = '致%s'%(1>2)
print(demostr) # 致False
demostr = '致%s'%([1,2,3])
print(demostr) # 致[1, 2, 3]

2. %d

语法: 只接收数字类型%d%(Number)

# 整型
numberStr = '只接受数字类型%d'%(269)
print(numberStr) # 只接受数字类型269
# 浮点型
doubleStr = '只接受数字类型且输出为整数(向下取整)%d'%(99.9)
print(doubleStr) # 只接受数字类型且输出为整数(向下取整)99

# 其他类型则会报错
numberStr = '只接受数字类型%d'%('哈哈哈')
print(numberStr) # TypeError

3. %f

语法：`只接受数字类型%f'%(Number) 其中整型会保留六位小鼠

floatStr = '只接受数字类型%f'%(269)
print(floatStr) # 只接受数字类型269.000000
#有小数的依然保留六位
floatStr = '只接受数字类型%f'%(269.9)
print(floatStr) # 只接受数字类型269.000000
#超过六位,看第七位，第七位大于5则第六位进1且舍去剩余位数
## 进1
floatStr = '只接受数字类型%f'%(269.1111116)
print(floatStr) # 只接受数字类型269.111112
## 舍去
floatStr = '只接受数字类型%f'%(269.1111115)
print(floatStr) # 只接受数字类型269.111111  

9. F/f 表达式

name = 19
mystr = F'我的名字是{name}'
print(mystr) # 我的名字是19

未完待续

以上。