String Assignment
Single quotation mark assignment
a = 'this is a string' print(a) # this is a string```
Double Quote Assignment
a = "this is a string" print(a) # this is a string
Assignment of a three-quote string to a variable (multiple lines)
Retains the newline format of the string
# Triple Form a = '''this is a string''' print(a) # this is # a string #Triple-Double Form a = """this is a string""" print(a) # this is # a string
Intercept string or substring
String interception can be obtained from an index like a list, starting with 0
Intercept characters at specified locations (indexes)
a = "this is a string" print(a[0]) # Intercept the 0th "t" of string a
Gets all the characters after the specified position (index)
a = "this is a string" print(a[1:]) # Gets all the characters "his is a string" after the string a index is 1 and 1
Intercept all characters before the specified position (index)
a = "this is a string" print(a[:2]) # Gets the string a index of 2 but does not contain all the characters "th" before 2
Get all characters
a = "this is a string" print(a[:]) # Getting all the characters of string a is equivalent to print(a)
Gets the characters in a specified location (index interval)
a = "this is a string" print(a[1:3]) # Gets all the characters "hi" in the string a index from 1 to 3, where the interval is closed and open
Gets a single character in reverse position (index)
String index starts from 0 left-to-right and -1 right-to-left
a = "this is a string" print(a[-1]) # Gets the string "g" with an index of -1 for string a
Get all the characters before the reverse position (index)
a = "this is a string" print(a[:-1]) # Gets the character "this is a strin" under all other indexes except the string a index of -1
Gets all the characters in the reverse position (index interval)
a = "this is a string" print(a[-3:-1]) # Gets all the characters in the string a index from -3 to -2, following the open interval principle of "in" before and after the reverse
Basic use of strings (commonly labeled with *)
*strip()
Remove white space characters at the beginning and end
a = " this is a string " print(a.strip()) #The result is that the space before and after "this is a string" is removed
lstrip()
Delete blank characters at the beginning (left) (can be remembered as left + strip => lstrip)
a = " this is a string " print(a.lstrip()) #The result is that the spaces at the beginning (left side of the string) of "this is a string" are removed
rstrip()
Delete blank characters at the end (right) (can be remembered as right + strip => rstrip)
a = " this is a string " print(a.rstrip()) #The result is that the space at the end of "this is a string" (to the right of the string) is removed
lower()
String to lowercase
a = "This is a String" print(a.lower()) #The result is that the "this is a string" string is all lowercase
upper()
String to Uppercase
a = "This is a String" print(a.upper()) #The result is that "THIS IS A STRING" strings are all capitalized
capitalize()
Convert the first character of a string to uppercase
a = "this is a string" print(a.capitalize()) #The result is "This is a string"
title()
Converts the first letter of each word of a string to uppercase
a = "this is a string" print(a.title()) #The result is "This Is A String"
*index()
- index(str): Gets the index of the first occurrence of a specified character within a string
- index(str,start,end): Gets the index of the first occurrence of a specified character within a specified index interval within a string
a = "this is a string"
print(a.index("h"))
#Result is 1,'H'has only one in string a and index is 1
print(a.index("i"))
#The result is 2,'i'has three in string a, but the index() method returns the first index to appear
print(a.index("k"))
#When using the index() method to find a character that does not exist in the original string, the method will fail
print(a.index("i",0,6))
#The result is 2,'i'has two indexes in the index interval [0,6] of a, but the index() method returns the last index that appears for the first time in the specified interval
*rindex()
The index method operates similarly, but returns the index of the last matching string
a = "this is a string"
print(a.rindex("i"))
#The result is 13,'i'has three in string a, and the last index is 13
print(a.rindex("i",0,6))
#The result is 5,'i'has two in the [0,6] interval of string a, and the last index in the specified interval is 5
print(a.rindex("k"))
#When using the rindex() method to find a character that does not exist in the original string, the method will error
*find()
The find and index methods are basically the same.
The only difference is that index does not find an error
a = "this is a string"
print(a.find("h"))
#Result is 1,'H'has only one in string a and index is 1
print(a.find("i"))
#The result is 2,'i'has three in string a, but the find() method returns the index that first appears
print(a.find("k"))
#When using the find() method to find a character that does not exist in the original string, the method does not error and the return value is -1
print(a.find("i",0,6))
#The result is 2,'i'has two indexes in the index interval [0,6] of a, but the find() method returns the last index that appears for the first time in the specified interval
*rfind()
The last occurrence of the returned string, or -1 if there is no match
a = "this is a string"
print(a.rfind("i"))
#The result is 13,'i'has only three in string a, and the last index is 13
print(a.rfind("k"))
#When using the rfind() method to find a character that does not exist in the original string, the method does not error and returns a value of -1
print(a.rfind("i",0,6))
#The result is 5,'i'has two indexes within the index interval [0,6] of a, but the rfind() method returns the last index that appears within the specified interval
*split()
Returns the list type by splitting the string according to the specified separator
a = "this is a string"
print(a.split(" "))
#Split string a into spaces, resulting in ['this','is','a','string']
print(a.split("k"))
# If the split string does not exist in the original string, only one element in the list returned by the group is a
# The result is ['this is a string']
*replace()
Replaces all characters in a string with the specified character
a = 'this is a string'
print(a.replace("i","k"))
#The result is "thks ks a strkng"
print(a.replace("k","f"))
# When the character you want to replace does not exist in the original string, the original string does not change
# The result is this is a string
*count()
Calculates the number of occurrences of a specified string in a string
a = 'this is a string'
print(a.count("i"))
# The result is that 3 "i" occurs three times in a
print(a.count("k"))
# When the specified character does not exist in the original string, 0 returns
center()
Use the specified character (default space) to center and align.
center(num,str):
num is the total length of the aligned character
str is the specified alignment character
a = 'china' a1 = a.center(50) #The result is: china a2 = a.center(50,'*') #The results are: **********************************china*************************
*endswith()
Returns true if the string ends with the specified character and false by default
a = "this is a string"
print(a.endswith("g"))
# The result is True
print(a.endswith("ing"))
# The result is True
print(a.endswith("a"))
# The result is False
print(a.endswith("k"))
# The result is False
*startswith()
Determines whether a string begins with the specified character, returns True, and returns False by default
a = "this is a string"
print(a.endswith("t"))
# The result is True
print(a.endswith("th"))
# The result is True
print(a.endswith("a"))
# The result is False
print(a.endswith("k"))
# The result is False
*isalnum()
Determines whether all characters in a string are alphanumeric, returns True, and returns False by default
a = "this is a string" print(a.isalnum()) # The result is True a = "this is a string123" print(a.isalnum()) # The result is True a = "this - is a string" print(a.isalnum()) # The result is False
*isalpha()
The judgement character cannot be empty, and all characters are letters, yes returns True, and default returns False
a = "this is a string" print(a.isalpha()) # The result is True a = "this is a string123" print(a.isalpha()) # The result is False
*isdigit()
Determines whether a string contains only numbers, returns True if it is, or False if it is not
a = "123456" print(a.isdigit()) #The result is True a = "123 456" # The result is that False contains spaces
*isnumeric()
Determines whether a string contains only numeric characters, returns True, otherwise returns False
a = "123" print(a.isnumeric()) # The result is True a = "1.23" print(a.isnumeric()) # The result is a False with the character'.. (Point)
istitle()
Determines whether the string is in title format, returns True, otherwise returns False
(Whether the first character of a word is capitalized)
a = "This Is A String" print(a.istitle()) # The result is True a = "this Is A String" print(a.istitle()) # The result is False
*islower()
Determines whether all lowercase cases are True or False
a = "this is a string" print(a.islower()) # The result is True a = "this Is A String" print(a.islower()) # The result is False
isupper()
Returns True if the string is all uppercase or False if it is not
a = "THIS IS A STRING" print(a.islower()) # The result is True a = "this Is A String" print(a.islower()) # The result is False
isspace()
Returns True if the string contains only spaces, or False if it does not.
a = " " print(a.isspace()) # The result is True a = "1 2 " print(a.isspace()) # The result is False a = "" print(a.isspace()) # The result is False
*len(str)
Get the length of the string
a = "this is a string" print(len(a)) # The result is 16
*join()
Combines an ordered list of characters specified into a new string
a = ["this","is","a","string"]
print(" ".join(a))
#The result is "this is a string"
print("#".join(a))
#The result is "this#is#a#string"
max()
Gets the largest letter in a string
a = 'abcdfefdga' print(max(a)) # The result is "g"
min()
Gets the smallest letter in a string
a = 'abcdfefdga' print(min(a)) # The result is "a"
zfill()
Returns a string of the specified length to the right, preceded by 0
a = "1" print(a.zfill(3)) #The result is "001"
*format()
String Formatting
output
a = "178.5"
print("My height is {0}cm".format(a))
# The result is "My height is 178.5cm"
'{:.2f}'.format()
Keep two decimal places
a = 178.5
print("My height is %scm" % '{:.2f}'.format(a))
#The result is My height is 178.50cm
'{:+.2f}'.format()
Keep two decimal places signed
a = -178.5
print("length is %s" % '{:+.2f}'.format(a))
#The result is length is -178.50
'{:.0f}'.format()
Do not keep decimals
a = 178.5
print("My height is %scm" % '{:.0f}'.format(a))
#The result is My height is 178cm
'{:x>5d}'.format()
Left padding, 5 for total length after padding, 0 for padding characters, support customization
a = '{:0>5d}'.format(123)
print(a)
#The result is "00123"
'{:x<5d}'.format()
Right padding, 5 for total length after padding, 0 for padding character, support customization
a = '{:0<5d}'.format(123)
print(a)
#The result is "12300"
'{:,}'.format()
Comma as separator, often used in thousands of quantities
a = '{:,}'.format(123456789)
print(a)
#The result is "123,456,789"
'{:.2%}'.format()
Percentage format
a = 0.123
print('{:.2%}'.format(a))
# The result is "12.30%"
a = 0.12345
print('{:.2%}'.format(a))
# The result is "12.35%" rounded
a = 0.12345
print('{:.3%}'.format(a))
# The result is "12.345%"
'{:>10d}'.format()
Right-aligned.10 is the total length after alignment
a = '{:>10d}'.format(12)
print(a)
# The result is "12"
'{:<10d}'.format()
Left-aligned.10 is the total length after alignment
a = '{:<10d}'.format(12)
print(a)
# The result is "12"
'{:^10d}'.format()
Center alignment.10 is the total length after alignment
a = '{:^10d}'.format(12)
print(a)
# The result is "12"
String traversal
Use a for loop to iterate through each character in a string
a = 'this is a string' for s in a: print(s) #The results are: t h i s i s a s t r i n g