Python strings, lists, dictionaries, and functions

One, the string

• In Python, the string does not need to be decomposed by a split in PHP explode or JavaScript, which can be used to get each character in a string directly from the subscript, starting from 0, if signed from a very long-expected, subscript starting from 1

str=‘abcde‘print(str[0])   #结果为：aprint(str[2])   #结果为：c

• The length of a string can be obtained through the len () function

• Slice: str[start position: End Position: Step]

• If you want to take a few characters (slices) in the string, you can add a colon solid line in the square brackets, a small start before the colon, a colon after the end of the subscript, intercept the colon before the beginning of the colon between the character, the tail does not pinch the head

str=‘abcde‘print(str[1:3])     #结果为：bcprint(str[2:3])     #结果为：cprint(str[1:0])     #结果为：bcde  冒号后为零，视为取到最后一个

• After the second colon , the number after the second colon is equal to the step, which is the subscript plus a few

Str = ' ABCDEABCDE 'Print(Str[1:8:2])#结果为: BdacPrint(Str[-1:0:-1])#结果为: EDCBAEDCBPrint(Str[-1::-1])#结果为: EDCBAEDCBAPrint(Str[::-1])#结果为: EDCBAEDCBAPrint(Str[::1])#结果为: abcedabced

• Common String Operations:

• Find (): Finds the first occurrence of a string in the target string from left to right, and cannot find return-1.

  str=‘hello world!‘print(str.find(‘o‘))    #结果为：4

• RFind (): Opposite to find, find from right to left.

• Index (): The function is the same as find, and the difference is that if the index is not found, an exception is thrown.

  • Rindex (): similarly.

  • COUNT (): Returns the number of occurrences of the lookup string in the target string, with no return 0.

  • Replace (' target string ', ' string to replace ', replaced several times)

  • Split (): With the Split function in JavaScript, if nothing is written in parentheses, the default is to cut the object with a space (very useful)

  • Join (): works with the Join function in JavaScript, but in a different form.

  = [‘aaa‘‘bbb‘‘ccc‘=‘#‘print(b.join(a))            #结果为：aaa#bbb#ccc

  • Capitalize (): Capitalize the first character of the string

  • Title (): Capitalize the first letter of each word of the string

  • StartsWith (): Checks whether the string starts with the target string

  • EndsWith (): Contrary to StartsWith

  • Lower (): lowercase all uppercase characters in the string

  • Upper (): Contrary to lower

  • Ljust (), Rjust (), center (): Within the length of the number filled in parentheses, left, right, center.

  • Lstrip (), Rstrip (), strip (): Trim with JavaScript

  • Partition (): The string is used to center the target string, divided into left and right three parts, return a tuple.

    str=‘hello world‘print(str.partition(‘o‘))   #结果为:(‘hell‘, ‘o‘, ‘ world‘)

  • Rpartition (): function with partition, take first from right to left.

  • Splitliness (): Split by line break.

  • Isalpha (): Determines if the target string is not a letter.

  • IsDigit (): Judging if the target is not a number.

  • Isalnum (): The goal is to determine whether there are both letters and numbers.

  • Isspace (): Determine if the target is not a space

Second, List

• Form:

= [‘张三‘‘李四‘‘王五‘]

• Additions to the list:

• Append ("What to add")

• Insert ("Location", "What to add")

• Merge list:

• Merge directly with the + sign

• Using the Extend () function

  = [‘张三‘‘李四‘"王五"= [‘赵六‘‘吴七‘=+ names2print(names3)                   #结果为：[‘张三‘, ‘李四‘, ‘王五‘, ‘赵六‘, ‘吴七‘]names1.extend(names2)print(names1)                   #结果为：[‘张三‘, ‘李四‘, ‘王五‘, ‘赵六‘, ‘吴七‘]

• Deletion of the list:
• Pop (): The last one in the pop-up list
• Remove (content): Deletes the first target content in the list

• del list name [subscript]

• Lookup of the list:
• "What to look for" in list name

• "What to look for" not in list name

• Traversal of the list:

forin 列表名:    print(temp)else:    print(‘end‘)    # for循环加上else，即为在for循环执行完成后，执行else部分

Third, the dictionary

• Form: dic = {key: value, Key: Value ...}, which is equivalent to an associative array in PHP, behaves in a form similar to a JSON object
• Deletion of the Dictionary del dictionary name [' Key Name ']
• Gets the data in the dictionary with get, and does not error when the corresponding content does not exist: dictionary name. Get (' Key name ')
• Functions of the Dictionary:
• Len (dic name): Gets the number of key-value pairs for the dictionary.
• Dic.keys (): Returns all keys in the dictionary.
• Dic.values (): Returns all values in the dictionary.
• Dic.items (): Converts the dictionary to Ganso.

Iv. Ganso

• (11,22,33) function is the same as the list, and differs in that Yuanju cannot be modified after it is defined.

Five, function

• Indefinite length function (Ganso):

  def*args):    print(a)    print(b)    print(args)example(12345678)    #结果为：1 2 (3, 4, 5, 6, 7)

• Indefinite length parameter (dictionary):

  def test(a, b, c = 33, *args, **kwargs):    print(a)    print(b)    print(c)    print(args)    print(kwargs)test(11, 22, 33, task = 99, done = 89)    #结果为：11 22 33 () {‘task‘: 99, ‘done‘: 89}

Python strings, lists, dictionaries, and functions