How to operate Python strings

1. String length

#strlen(str)　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
str= 'apples' 　　　　　 # Assign the string "apples" to the variable str
print (len (str))　　　#Print the length of the string

2. Find characters

#strchr(str1,str2)　　　#Find character function name
str1 = ' apples'　　　　
str2 = 'e'
result = str1.index(str2)　　　# Find the character str2
print (result)

3 in the string str1 .Copy string

#strcpy(str1,str2)　　　　#Copy string function name
str1 = 'apples'　　　　
str2 = str1　　　　　　#Assign string str1 to str2
str1 = 'bananas'　　　　　#Reassign the string value to str1
print (str2)

4. Connect the string

#strcat(str1,str2)　　　#Connection characters String function name
str1 = 'apples'
str2 = 'bananas'
str1 += str2　　　　　　 #String str1 is concatenated with string str2 and then assigned to str1
print (str1)

5. Case conversion in strings

str.lower() Case swap
str.capitalize() 　　　　 #Capitalize the first letter

#strupr(str)

str = 'abcdefgh'

str = str.upper()
print ( str)

#strlwr(str)

str = 'ABCdefgh'

str = str.lower()
print (str)

6. Reverse the string

#strrev(str)　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

str = 'abcdefg''　　　　

str = str[::-1]　　　　 # Index is from the beginning to the end, Three parameters - 1 means reverse order
print (str)

7. Find the string

#strstr(str1,str2)　　　　#Find the string function name

str1 = 'abcdefg'

str2 = 'cde'
print (str1.find(str2)) # Find the string str2 in the string str1

#Variable.find(

"What to find",[start position, end position]), the start position and the end position represent the range to be searched, and if empty, it means to search all. After the search is found, the position will be returned. The position is calculated from

0. If it is not found, -1 will be returned.

8. String replacement

str = 'abcabcabc'　　　　　

str=str.replace('a', '0')　　　　#Replace the character "a" in the string str with "0", and reassign it to str

print (str)

9. String alignment

str.ljust(n,[fillchar]) 　　　　 # Output n characters, str is left-aligned, and the missing part is filled with fillchar. The default is spaces.

str.rjust(n,[fillchar]) 　　　　　 # Same as above, right aligned

str.center(n, [fillchar]) 　　　　 # Same as above, centered

10. Others Function

str.count(char, [start, [end]]) 　　　　#Count the number of times the character char appears in the string str, you can set where to start and where to end

str.strip([chars]) #Remove all the characters before and after the character chars in str, which can be understood as replacing the chars before and after S with None

str.lstrip([chars]) #Remove the left part of the character chars

str.rstrip([chars]) 　　　　　　　 #Remove the right part of the character chars

str.split([sep, [maxsplit]])　　　　 #Use sep as the delimiter, divide str into a list, maxsplit means splitting The number of times, the default separator is the blank character

str.startswith(char)　　　　　　　　　#Whether it starts with char

str.endswith(char)　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

str.isalnum()　　　　　#str Whether it is all letters and numbers
Str.isalPha () #Str.isdigit () #Str.isdigit () #Str.isdigit () #Str.isspace () #Tr ##str.islower() 　　　　　　　　 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　cred Meshes _ The letters in #str are all lowercase
str.isupper() [ The first letter is capitalized



11. String slicing

str = 'abcdefghigklm′
str[0:3] 　　　 #Intercept the first to third characters# "abc"
str[:] 　　　　　　 #Intercept all characters of the string# "abcdefghigklm"
str[6:] 　　　　 #Intercept from the seventh character to the end# "higklm"
str[:-3] 　　　　 #Intercept from the beginning to before the third to last character# "abcdefghig"
str[2 ] 　　　　　　#Intercept the third character# "c"
str[-1] 　　 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　okaleg hand in the first character from the last to last## "m"
str[::-1] 　　　　 #String reverse order# "mlkgihgfedcba"
str[-3:-1] 　　　 #Intercept the third to last character and the characters before the first to last# "kl"
str[-3:] 　　　　 #Intercept the third to last character to the end# "klm"
str[:-5:-3] 　　　　#Truncate the last four characters in reverse order, and intercept every 2 characters# "mg"　　　

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