python 笔记 10.31

# 定义字符串
# 引导转义
print('let's learn Python')   #!!!!!!!!!
print("let's learn Python")
print('''let's learn Python''')

print("How do you spell the world "pyton"?")

print(r"\n换行;\b退格;\r回车")

# 格式化字符串
# 使用格式化
value = 25
format = "今年%d岁"
print(format % value)
print("今年%d岁" % value)
print("今年%f岁" % value)
# value = "周一"
# print（"今天是%d"%value)
value_1 = "周一"
print("今天是%s" % value_1)

print("今年%d岁,今天是%s" % (value,value_1))
#使用format()方法格式化
# str.format()
age = 25
string = "今年{}岁"
print(string)
print(string.format(age))
a = string.format(age)
print(a)        # string.format 返回值
print(string)   # string 没有改变
# f-string 格式化
string = f"今年{age}岁"
print(string)
print(f"年龄：{25}，性别：{"男"}")

# 字符串常见操作
# 查找str,find(). 返回索引位置
string = "python"
a = string.find("t")
a = "Python".find("t")
print(a)
# 替换str.replace(). 返回替换后的新字符串, 用字符串不变
string = "Hello world"
a = string.replace("o",'p',1)
print(a)
print(string)
# 分割 str.split() 返回由分割后的子串组成的列表
# str.split(sep=None,maxsplit=-1),分隔符sep,分割次数maxsplit. 不限制分割次数
string="apple,peach,banana,pear"
a= string.split(",")
print(a)
string = "2025-10-31 9:15:45"
a = string.string("0") # 分隔符会删掉
print(a)
a = string.split("-",1)
print(a)
# 拼接 str.join(), "+"
string = "Hello world"
symbol = "*"
a = symbol.join(string)
print(a)
print("Py"+"th"+"on")
print("-"*45) # 字符串乘法
# 删除
string="a!apple,peach"