Python 字符串方法 | 第一讲(find,rfind,startswith,endswith,islower,isupper,lower,upper,swapcase & title)
一些字符串的基础已经在下面这些文章里涵盖了:
重要的字符串方法将在这篇文章里讲解。
1. find(“string”, beg, end) 这个函数被用来在字符串中找到子字符串的开始位置。它有三个参数, 子字符串 , 起始索引( 默认为0) and 结束索引(默认为字符串长度).
- 如果在字符串中没有找到给定的子字符串,那么会返回-1。
- 它会返回子字符串的开始位置索引
2. rfind(“string”, beg, end) :- 这个函数和 find()有几乎相同的功能, 但是它返回子字符串的结束位置索引 。
# Python code to demonstrate working of # find() and rfind() str = "geeksforgeeks is for geeks" str2 = "geeks" # using find() to find first occurrence of str2 # returns 8 print ("The first occurrence of str2 is at : ", end="") print (str.find( str2, 4) ) # using rfind() to find last occurrence of str2 # returns 21 print ("The last occurrence of str2 is at : ", end="") print ( str.rfind( str2, 4) )
Output:
The first occurrence of str2 is at : 8 The last occurrence of str2 is at : 21
3. startswith(“string”, beg, end) :- 如果字符串是以指定的子字符串开头的,那么返回 True,否则返回 False。
4. endswith(“string”, beg, end) :- 如果字符串是以指定的子字符串结尾的,那么返回 True,否则返回 False。
# Python code to demonstrate working of # startswith() and endswith() str = "geeks" str1 = "geeksforgeeksportal" # using startswith() to find if str # starts with str1 if str1.startswith(str): print ("str1 begins with : " + str) else : print ("str1 does not begin with : "+ str) # using endswith() to find # if str ends with str1 if str1.endswith(str): print ("str1 ends with : " + str) else : print ("str1 does not end with : " + str) )
Output:
str1 begins with : geeks str1 does not end with : geeks
5. islower(“string”) :- 如果字符串中所有字符都是 小写的 ,那么返回 True,否则返回 False。
6. isupper(“string”) :- 如果字符串中所有字符都是因为大写的,那么返回 True,否则返回 False。
# Python code to demonstrate working of # isupper() and islower() str = "GeeksforGeeks" str1 = "geeks" # checking if all characters in str are upper cased if str.isupper() : print ("All characters in str are upper cased") else : print ("All characters in str are not upper cased") # checking if all characters in str1 are lower cased if str1.islower() : print ("All characters in str1 are lower cased") else : print ("All characters in str1 are not lower cased")
Output:
All characters in str are not upper cased All characters in str1 are lower cased
7. lower() :- 这个函数返回一个所有字符都 被转化成小写字母的新字符串。
8. upper():- 这个函数返回一个所有字符都被转化成大写字母的新字符串。
9. swapcase() :- 这个函数被用来转换字符串中每一个字符的大小写。
10. title() :- 这个函数把字符串中的每个单词首字母转换为大写,其余则为小写。
# Python code to demonstrate working of # upper(), lower(), swapcase() and title() str = "GeeksForGeeks is fOr GeeKs" # Coverting string into its lower case str1 = str.lower(); print (" The lower case converted string is : " + str1) # Coverting string into its upper case str2 = str.upper(); print (" The upper case converted string is : " + str2) # Coverting string into its swapped case str3 = str.swapcase(); print (" The swap case converted string is : " + str3) # Coverting string into its title case str4 = str.title(); print (" The title case converted string is : " + str4)
Output:
The lower case converted string is : geeksforgeeks is for geeks The upper case converted string is : GEEKSFORGEEKS IS FOR GEEKS The swap case converted string is : gEEKSfORgEEKS IS FoR gEEkS The title case converted string is : Geeksforgeeks Is For Geeks
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