'' '' '' '' ' Defined in the Python 1 is an explanatory weak type level programming language Advanced here is relatively lower (for example: assembly language, etc.) high-level and low-level programming language programming language, the difference between a former closer to human understanding - grammar letters 2, which is closer to understanding calculator - byte code, binary characteristics of python 2 life is short, I use python concise Why learn python 3 hobby, artificial intelligence , machine learning, large data . 4 python first program print ( 'hello world') Method 1: enter in cmd python, the interactive command line, enter the above statement, enter mode 2: Create a local disk d hello. py file, copy the file .py to the above statement, after storage in cmd, into the disc d, Run python hello.py Embodiment 3: After the above statements are written PyCharm, RUN . 5 the concept of variable variable program is running intermediate value generated --temp (temporary attribute, open a memory for storing a value) 1, memory space name is the name of the variable naming 6 variables: 2, save memory space Value is the value of the variable For example: a = 10 variable name is the value of a variable is 10 1, consists of: numbers, letters, underscores 2, beginning: can not start with a number 3, Keywords: Keywords can not be, for example: List 4, length: not too long 5, Chinese: Chinese is not 6, meaningful: to interesting (a look at the name, you probably know the meaning of the variables indicated) 7, case: strictly case-sensitive 8, writing: recommended underlined or hump law named underlined: hello_world (between words, separated by an underscore) hump method: the helloWorld (not capitalized first letter, starts the second word, the first letter capitalized) data type of the variable 7 an integer int + - * / // BIT_LENGTH () 2 string STR 1, represented by '' \ '' \ ' "" Precautions: \ escape herein indicates a single quotation marks '' two pairs of marks "" 3 three single quotes 2, repeated * 3 + stitching 4,% s format'' ' ' '' 4 three double quotation marks "", "", "" 5, indexing and slicing S1 [ start: end:step] left and right open closed 1 start start index - subscript 2 end end index - subscript (not eligible) . 3 Start step (not written, is 1 by default) 6, common built-in method 1 Upper () to uppercase 2 strip () to remove the string ends of the blank strip ( 'ab') removing the ends of the string 'ab &' 3 replace (Old, new new, COUNT) parameter 3 from left to right COUNT represents the number of alternative parameters 3 is not written, the default is to replace all 4 split () splits the string into several sub-strings, each substring as elements of the list, returns a list of default separator is a space split ( '_') delimiter is underlined 5 '_'. join () the parameter iterable strings through a connector '_' splice into strings written: 'connector' .join (iterable) Note point: . 1 Iterable the elements must be str, int is not Method 2 join is not built string 6 startswith () written: s1.startwith ( 'a') action: determining whether the string starts with the letter 'A' . 7 Find index COUNT written: s1.find ( 'a') acting: Find character string s1 'a', returns the index number; if not, it returns -1 - more robust recommended wording: s1.index ( 'a') acting: Find the character string s1 'a ', returns the index number; if not, then an error writing: s1.count (' a ') role: from statistics character strings s1' number of occurrences of a ', the number of int return to appear if it is 0, representatives not found (there are functions to find) 8 isdigit () writing: s1.isdigit () function: to determine whether a string is in digital form, it is, returns True 9 len () writing: len (s1) Action: Returns the length of the string 7, string Iterable for I in S1: loop (BREAK Continue) the else: Pass . 8, the encoding string 1 ascii 8 bits 1 byte 2 gbk gb2312 16 GB code bit 2 of byte 3 unicode Unicode 32 4 byte 4 utf-8 Unicode variable . 1 English one byte characters 8 2 2 16 European character bytes (German, French, Spanish, etc. character) 3 24 3 Chinese character byte string bytes into byte encoded coding - encryption - compression after byte string decoded into decoded - - after extracting bytes.decode () # decoder 3, bool Boolean type values: True False role: for determining the type of conversion : False: 0 or empty ( '' [ ] () {} set () None) } set () None) empty string, an empty list, empty tuple, empty dictionary, a null set, null None Note: space, \ r \ n \ t are true true: above, in addition to others are true Precautions: type conversion may be used directly Analyzing False Notes: examples. 1 content1 = iNPUT ( 'enter your name: ") # input string if content1: # Analyzing If you do not enter an empty content, directly enter, to suggest - you do not pay attention to the name of the point: the results of the following line and not the same as # if content1 == '': # If you do not enter content directly enter, print - your name is the print ( 'your name is', content1) the else: # If you do not enter anything, this is an empty string content1 print ( 'you no name') example 2 of Li1 = [, 2, 3] IF of Li1: # here is deciding whether the list is empty, and the following line equivalent IF in Li1 == # []: Print (in Li1) the else: # print ( 'Empty list ') . 4, in list represents: [], are separated by commas between the elements of the concept: a listing is a container that can store any data type array array and other development languages similar features: 1, the list is variable 2, the indexing and slicing function list common operations: 1 by 1 the append (element values) in the list of additional elements rearmost 2 insert (i, element values) in the list before the specified position of the insertion element 3 extend (iterable) the elements in iterable in turn added to the original list of 2 deleted 1 pop () parameter does not write, the default is to remove the last element Parameter may specify the index number, to remove 2 remove the element Removes the specified value 3 del slice or delete a single 4 Clear 1 pop Empty element 3 to change an index according to - subscript modified slice modified single index modification 4 check 1, a single index value 2, for looping through 01 list - Summary adding elements 1 at the end of the append is to add a new element - the most commonly 2 insert is before the specified location to insert a new element 3 extend is sequentially added iterable elements to the original list of 02 list - delete an element summary parameters: element value (not position) effect: Deletes the specified element value Without parameters, default to the last element of the deletion list, and acquires the last element to be deleted specified parameters, to delete the specified location - the element the element index number, and acquires the specified location of the deleted 2 Remove wording: del dictionary name [key] Del 3 . 1 Parameters: single location - index wording: del list (position) effect: to delete a single location element 2 parameters: Slice written: del list (sliced) action: a plurality of slice locations remove elements 3, arguments: name written: del list name role: delete the entire list, recovery of memory space (empty clear and are different) 4 parameters: key dictionary function: delete the specified key dictionary corresponding key-value pair summary, the role of del 1, individual elements can be deleted position 2, you can remove a plurality of slice elements 3 can delete the entire list, recovering memory space 4, not only a list, also applies to the dictionary 4 clear parameters: null wording: li1.clear () function: to clear the elements of the list into an empty list empty - a list of the memory space is not recovered (and del li1 not the same) list 03 - Summary modifications element 1 position modified single - single element Review written: li3 [1] = 'james ' effect: the designated location - a list of index modifications individual elements 2, a plurality of elements to modify the slice 12 elements change elements into a [ 'james', 'kevin'] 32 elements into three elements the correct wording: li3 [1: 3] = [' james'] Error writing: li3 [1: 3] = 'james' attention point 22 element into two elements written: li3 [1: 3] = 3 sort () to sort the list of elements to sort in ascending order by default, the list itself modified 4 reverse () inverted Wording: LI3 [1:. 3] = [ 'James', 'Kevin', 'Lucy'] 04 List - Summary of query elements in a single query - single value - according to a single location - index - subscript plurality of query 2 - multiple values - in accordance with sections 3 all inquiries - all values -for loop through 5, other common operations 1 count () counts the number of calculations appear in the list an element 2 index () lookup returns an element in the list position - the index - index to the list of elements is reversed, modify the list itself 6, the process loops through the list, you can not remove elements, because it involves moving element solution: the elements to be deleted, added to the new list, circulating a new list, delete the old list 7, the depth of copying and assignment 1 = assignment, two variables point to the same memory address, different variables but different aliases for the same memory address 2, shallow copy, copy only the first layer (second layer and above point to the same memory space is not achieved copies) li1.copy () in Li1 [:] test whether the memory space is a way: See the value of the variable id 3, deep copy, copy only the first layer, the second layer and above are copied li1.deepcopy () extension: in other programming languages (such as: Java), named clone, also cloned into the depth shallow deep copy of analogy 1, a shallow copy is separate from the first memory layer, the second layer and above the same memory space is a [the results for the cycle if the judge] example: - a first separate layer, upper layer, and a second change has changed The first layer is the family financial couples AA second layer is a joint account set up by husband and wife family 2, a deep copy is separate from the first memory layer, the second layer and above separate memory space - each is completely independent analogy: Family couple Finance complete AA, does not have a joint account 8, list comprehensions written = LI7 [l, 2,3] # demand: the odd list, the number of squares which becomes LI8 = [I * for I I I in LI7% 2 == IF. 1] Print (LI8) # [. 1,. 9 ] '' '