python内置方法（重点）

# 任意数据对象.方法()实现对数据的某种操作
# 不同数据类型对象支持不同方法
# 字符串类型对象支持哪些方法

s1 = "yuan"
s2 = "RAIN"
# (1) upper方法和lower方法
s3 = s1.upper()
s4 = s2.lower()
print(s3) # "YUAN"
print(s4) # "rain"


s5 = "hello yuan"
s6 = "hi world"
# (2) startswith和endswith：判断字符串是否以什么开头和结尾
print(s5.startswith("hello")) # True
print(s6.startswith("hello")) # False
print(s6.startswith("hi wor")) # True
print(s6.endswith("hi wor")) # False

# (3) isdigit(): 判断字符串是否是一个数字字符串
s7 = "123"
s8 = "123A"
print(s7.isdigit()) # True
print(s8.isdigit()) # False
s9 = "123SAA%#"
print(s9.isalnum()) # False 不能包含特殊符号

# (4) strip(): 去除两端空格和换行符号

s10 = " I am yuan "
print(s10)
print(s10.strip())
name = input("请输入姓名>>").strip()
print(name)

# (5) split分割方法: 将一个字符串分割成一个列表
s11 = "rain-yuan-alvin-eric"
print(s11.split("-")) # ['rain', 'yuan', 'alvin', 'eric']

# (6) join方法: 将一个列表中的字符串拼接成一个字符串
names_list = ['rain', 'yuan', 'alvin', 'eric']
s12 = "-".join(names_list) # 用什么分隔符拼接names_list列表
print(s12,type(s12)) # "rain-yuan-alvin-eric"

【5】类型转换

i = int("3")
print(i,type(i)) # 3 <class 'int'>

s = str(3.14)
print(s,type(s)) # 3.14 <class 'str'>