字符串常用函数

# ### 字符串的相关函数
# *capitalize 字符串首字母大写 
strvar = "how are you"
res = strvar.capitalize()
print(res)

# *title 每个单词的首字母大写 
strvar = "how old are you"
res = strvar.title()
print(res)

# *upper 将所有字母变成大写
strvar = "How Old Are You"
res = strvar.upper()
print(res)

# *lower 将所有字母变成小写 
res = strvar.lower()
print(res)

# *swapcase 大小写互换 
strvar = "How old Are You"
res = strvar.swapcase()
print(res)

# *len 计算字符串的长度 
strvar = "python32真热"
res = len(strvar)
print(res)

# *count 统计字符串中某个元素的数量 
"""count(字符,[开始值,结束值])"""
strvar = "真热真热呀"
# res = strvar.count("真")     # 2
# res = strvar.count("热",2)   # 1
# res = strvar.count("热",2,3) # 只有真这个字符 没有热
print(res)

# *find 查找某个字符串第一次出现的索引位置  (推荐)
"""find(字符,[开始值,结束值])"""
strvar = "To be or not to be that is a question"
res = strvar.find("to")
res = strvar.find("be",4)
# 如果find 返回的是 -1 代表没找到
res = strvar.find("be",4,10) # 4 ~ 9
print(res)

# *index 与 find 功能相同 find找不到返回-1,index找不到数据直接报错
"""
res = strvar.index("be",4,10) 
print(res)
"""

# *startswith 判断是否以某个字符或字符串为开头 
"""
startswith(字符,[开始值,结束值])
endswith(字符,[开始值,结束值])
"""
strvar = "To be or not to be that is a question"
res = strvar.startswith("To")
res = strvar.startswith("To",10)
print(res)

# *endswith 判断是否以某个字符或字符串结尾 
res = strvar.endswith("question")
res = strvar.endswith("is",-14,-11) #  is
print(res)


# ### is系列
# *isupper 判断字符串是否都是大写字母 
strvar = "HOW  A  YOU"
res = strvar.isupper()
print(res)

# *islower 判断字符串是否都是小写字母 
strvar = "asdf - as"
res = strvar.islower()
print(res)

# *isdecimal 检测字符串是否以数字组成  必须是纯数字
strvar = "abcdefg"
strvar = "2134234.123"
strvar = "2134234"
res = strvar.isdecimal()
print(res)


# *split 按某字符将字符串分割成列表(默认字符是空格)  ***
strvar = "you can you up no can no bb"
lst = strvar.split()
strvar = "you#can#you#up#no#can#no#bb"
lst = strvar.split("#")
print(lst)

# *join  按某字符将列表拼接成字符串(容器类型都可)    ***
lst = ['you', 'can', 'you', 'up', 'no', 'can', 'no', 'bb']
strvar = " ".join(lst)
strvar = "#".join(lst)
print(strvar)

# *replace 把字符串的旧字符换成新字符  ***
"""字符串.replace('旧字符','新字符'[, 限制替换的次数])"""
strvar = "范冰冰爱不爱我,爱我,不爱我,爱我,不爱我"
res = strvar.replace("不爱我","爱我")
# 选择替换的次数
res = strvar.replace("不爱我","爱我",1)
print(res)

# *strip  默认去掉首尾两边的空白符  ***
"""空白符 空格 \n \t \r ... """
strvar = "     周润发  "
res = strvar.strip()
print(strvar)
print(res)

# *center 填充字符串,原字符居中 (默认填充空格)
"""center(字符长度,填充符号)"""
strvar = "赵世超"
res = strvar.center(10)
# res = strvar.center(10,"*")
print(res)