python字符串

字符串定义：是以单引号或双引号括起来的任意文本 'abc' "abc"（字符串不可变） 创建字符串

str1 = "sunck is a good man!"
str3 = "sunck is a nice man!"
str5 = "sunck is a handsome man!"
print(str1)
print(str3)
print(str5)

字符串运算 字符串连接

str6 = "sunck is a "
str7 = "good man"
str8 = str6 + str7
print(str6)
print(str7)
print(str8)

字符串重复输出

str9 = "good"
str10 = str9 * 3
print(str10)

访问字符串中的某个字符 通过索引下标查找字符串，索引重0开始 字符串名[下标]

str11 = "this is a good man!"
for i in range(len(str11)):
    print(str11[i],end = '\t')

取字符串中的一部分

str13 = "this is a good man!"
str15 = str13[8:15]
str16 = str13[:5]
print(str15)
print(str16)

判断字符串中是否存在某一个值

str18 = "this is a good man!"
print("good" in str18)
print("good1" in str18)

格式化输出

• %d %s %f 占位符
• %-8d 左对齐，占8位
• %8d 右对齐，占8位
• %.4f小数点后面精确4位，支持四舍五入

num = 10
str19 = "this is a good man!"
f = 10.1234789
print("num = ",num,"str19 = ",str19)
print("num = %8d\nstr19 = %s\nf = %.4f"  %(num, str19, f)

len(str)字符串的长度

str19 = "this is a good man!"
print(len(str19))

lower(str) 转换字符串中大写字母为小写字母

str20 = "SUNCK is a good Man"
print(str20.lower())
print(str20)

upper()转换字符串中大写字母为大写字母

str20 = "SUNCK is a good Man"
print(str20.upper())
print(str20)

swapcase()将大写转成小写，小写转成大写

str22 = "SUNCK is a gOOd mAn"
print(str22.swapcase())
print(str22)

capitalize()首字母大写，其他小写

str23 = "SUNCK is a gOOd mAn"
print(str23.capitalize())
print(str23)

title()每个单词的首字母大写

str23 = "SUNCK is a gOOd mAn"
print(str23.title())
print(str23)

center(width,fillchar) 返回一个指定宽度的居中字符串，fillchar为填充的字符串写

str25 = "kaige is a good man"
print(str25.center(40,"*"))
print(str25)

ljust(width[,fillchar]) #返回一个指定宽度的左对齐中字符串，fillchar为填充的字符串，默认是空格填充

str25 = "kaige is a good man"
print(str25.ljust(40))
print(str25.ljust(40,"*"))
print(str25)

rjust(width[,fillchar]) #返回一个指定宽度的右对齐中字符串，fillchar为填充的字符串，默认是空格填充

str25 = "kaige is a good man"
print(str25.rjust(40))
print(str25.rjust(40,"*"))
print(str25)

返回一个指定宽度的右对齐中字符串，默yong0补齐

str28 = "kaige is a good man"
print(str28.zfill(40))
print(str28)

count(str[,start][.end]) #返回字符串中str出现的次数指定范默认从头到尾

str29 = "kaige is a good man"
print(str29.count("very"))
print(str29.count("good",1,len(str29)))
print(str29)
count(str[,start][.end])

find(str[,start][,end])

• 从左向右检测str字符串是否包含在字符串中，可以指定范围
• 默认是从头到尾，得到第一次出现的下标，没有返回-1

str30 = "kaige is very very very a good man"
print(str30.find("very"))
print(str30.find("good"))
print(str30.find("very",15,len(str30)))

#rfind(str[,start][,end])

• 从右向左检测str字符串是否包含在字符串中，可以指定范围
• 默认是从尾到头，得到第一次出现的下标，没有返回-1

str30 = "kaige is very very very a good man"
print(str30.rfind("very"))
print(str30.rfind("good"))
print(str30.rfind("very",0,15))

index(str,srart=0,end=len(str))

• fing()一样，只不过如果str不存在的时候会报一个异常

str31 = "kaige is very very very a good man"
print(str31.index("good"))

lstrip()截掉字符串左侧指定的字符，默认是空格

• rstrip()截掉字符串左侧指定的字符，默认是空格

tr33 = "****************kaige is  very a good man*******************"
print(str33.lstrip("*"))
print(str33.rstrip("*"))
print(str33.strip("*"))

• 不乱于心，不困于情。
• 不畏将来，不念过往。
• 如此，安好。