Basic methods of strings in python

The use of String

1. String concatenation String concatenation
usage 1 ( instruction ): StringObject1+StringObject2

str1 = 'I am Iron man'
str2 = 'i am sprider man'
str3 = str1 + str2
print(str3)
print(str1,'and','str2')

Usage 2: character.join(StringObject1)

str1 = '192.168.0.0'
print(':'.join(str1.split('.')))

######################
192:168:0:0

(split is the usage of string cutting, which will be explained later)

2. Repeat string
usage ( instruction ): StringObject*number

str1 = 'hello world'
print(str1*3)

3. Use the following table to find the corresponding characters (the subscript starts from 0 ) Use subscripts to find the string (the subscripts start with zero)
Usage ( instruction ): StringObject[subscript]

str1 = 'china'
print(str1[2])

##########################
i

4. Intercepting string fragments Intercepting string
Usage ( instruction ): StringObject[start:stop]
1. Intercept from the given subscript to before the termination subscript ( from the subscript to the other subscript)

str1 = 'world'
print(str1[2:4])

#####################
rl

2. Cut from the head to before the given subscript ( from the head of the string to the subscript )

str1 = 'world'
print(str1[:3])

#########################
wor

3. From the given subscript to the end ( from the subscript to the tail of the string )

str1 = 'world'
print(str1[1:])

################
orld

5. Determine whether a character is in the corresponding string Determines whether a character in the string
Usage ( instruction ): in StringObject/not in StringObject

str1 = 'world'
print('o' in str1)
print('ld' not in str1)

Six, formatted output Formatted print

str1 = 'world'
print('str1=%s,num=%d'%(str1,2))

7. Convert a string to a valid operation for evaluation Converts a string to a valid operation for evaluation
Usage ( instruction ): eval(StringObject)

str1 = '12-3'
print(str1)
print(eval(str1))

######################
12-3
9

8. Return the length of the string Return the length of the string
Usage ( instruction ): len(StringObject)

str1 = 'world'
print(len(str1))

Nine. Change the string case Change the string case
1. All uppercase/lowercase ( upper/lower )
instruction : StringObjet.upper()/StringObject.lower()

str1 = 'WOrld'
print(str1.upper())
print(str1.lower())

2. The string case interchange
instruction : StringObject.swapcase()

str1 = 'WOrld'
print(str1.swapcase())

3. Capitailze the first character
instruction : StringObject.capitalize()

str1 = 'hello world'
print(str1.capitalize())

#########################
Hello world

4. Capitalize the first letter of a single string (note: it is different from usage 3)
instruction : StringObject.title()

str1 = 'hello world'
print(str1.title())

#########################
Hello World

10. Find the corresponding string, the return value is the subscript Find the corresponding string and return the string`s subscript
Usage ( instruction ): StringObject.find(StringObject(start,stop))

str1 = 'world'
print(str1.find('or',0,len(str1)))

11. Cut off the specified character (default space) Remove the specified character from the string (the default spaces)
Usage 1 ( instruction ): StringObject.strip/lstrip/rstrip

str1 = ' h ell o wor l d !!'
print(str1.strip())
#截掉最左侧指定字符
print(str1.lstrip(' '))
#截掉最左侧指定字符
print(str1.rstrip('!'))

###############################
h ell o wor l d !!
h ell o wor l d !!
 h ell o wor l d 

Usage 2: StringObject.split() (the return value is a list)

a = '192.168.0.0'
print(a.split())

##################
['192', '168', '0', '0']

12. Return the specified width position string
Usage ( instruction ): StringObject.center/ljust/rjust(width,fillchar)

str1 = 'world'
#居中
print(str1.center(20,'*'))
#左对齐
print(str1.ljust(30,'*'))
#右对齐
print(str1.rjust(40,'*'))

#####################
*******world********
world*************************
***********************************world