Today content summary:
1. The function portion
01.-defined functions in three ways
* No function parameter
# not need to receive incoming external parameters
* There function parameter
# needs to receive external parameters passed
Note: one more or less a parameter passing is not
* Empty function
# encounter some of the more difficult to achieve the function, it can cause temporarily unable to continue writing code.
# It is generally in the production development, will implement all the functions defined as empty function.
' # # Nullary function # # not need to receive incoming external parameter # DEF foo (): # Print (' .. from foo ') # foo () # # # # # has a function parameter # # needs to receive external incoming parameter # DEF Login (User, pwd): # # Print (User, pwd) # # # # # a parameter passing one more or less non- # Login ( 'Tank', '123') # # Login ( ' tank ',' 123 ', 111 ) # multiple, given # # Login (' Tank ') # low, given # # # = 10 X # # Y = 20 is # # # # IF X> Y: # # # # Print (X) # # # # the else: # # Print (Y) # # # compare two operand size # DEF MAX2 (X, Y): # # IF X> Y: # # Print (X) # # the else: # Print (Y) # # MAX2 (10, 30) #
02. The return value of the function
when calling the function, the function generates results need to receive the internal body, the return value is returned.
# def max2(x, y): # # if x > y: # # return x # # else: # # return y # # res = max2(10, 5) # # print(res)
03. function object
refers to the name of the function at the memory address.
# DEF FUNC (): # Pass # # # Print (FUNC) # <function FUNC AT 0x101dd2e18> # # # # FUNC () # # DEF func2 (): # Pass # # # the function object, passing in the dictionary # = {dict1 # '. 1': FUNC, # '2': func2 # } # # Choice = iNPUT ( 'enter number function:') Strip (). # # # == IF Choice '. 1': # # FUNC () # # elif Choice == '2': # # func2 () # # # # # If the user selects the object corresponding to the key value of the function, the function is called # IF Choice in dict1: # dict1 [Choice] () # dict1 [ '. 1']
04. nested functions:
nested definitions:
in the function, defined functions.
Nested call:
# Function nested definitions # # DEF func1 (): # # Print ( 'func1 ...') # # DEF func2 (): # Print ( 'func2 ...') # # DEF func3 (): # Print ( 'func3 ...') # # # .... # # return func3 # # return func2 # # internal function by the function value, the function call # func2 = func1 () # func3 = func2 () # func3 () # # # # nested function calls # DEF func1 (): # # print('func1...') # # def func2(): # print('func2...') # # def func3(): # # print('func3...') # # # .... # # func3() # # func2() # # func1()
05. namespace
python interpreter comes with: built-in namespace
from within the definition of py file, wore the leftmost defined: global name space
defined inside a function: local name space
= name ' Tank ' DEF func1 (): # name = 'Tank' Print () DEF func2 (): Print ( ' func2 ... ' ) # Print (name, 'global print') func1 ()
2. The template package
# Import module name
Import B
# from
# B module to import a file
# automatically execute the code in a file
# Import module name Import B # from # import a file module B # code that automatically performs a file from B Import a # the __name__: of Ba # a
3. Built-in templates
01.time
02.os
03.sys
04.json
'' '' '' '' ' Common modules (built-in modules) ' '' # time # Import time introducing time module # # # obtain a timestamp # Print (the time.time ()) # # # Wait 2 seconds # time. SLEEP (2) # # Print (the time.time ()) # OS Import OS # operating system files interact # determines whether the file exists tank.txt # Print (os.path.exists ( 'tank.txt') ) True # # Print (os.path.exists ( 'tank1.txt')) False # # Print (os.path.exists (r'D: \ python_files \ day03 \ tank.txt ')) True # # # # Get the current file in the root directory #Print (os.path.dirname (__ file__)) # D: / python_files / day03 # SYS Import SYS # get python file path environment variable # Print (sys.path) # # to add items to the root directory environment variable in # sys.path.append (os.path.dirname (__ file__)) # Print (the sys.path) # JSON Import JSON # USER_INFO = { # 'name': 'Tank', # 'pwd': '123' # } # dumps: sequence of # 1, to switch the dictionary json data # 2, then the data is converted into a string json # RES = json.dumps (USER_INFO) # Print (RES) # Print (type (RES)) # # with Open ( 'user.json', 'wt', encoding = 'UTF-. 8') AS F: # f.write (RES) # loads: deserialize # JSON. loads () # . 1, the data files into memory json # with Open ( 'user.json', 'R & lt', encoding = 'UTF-. 8') AS F: # # reading obtained string # reached, f.read = RES () # # Print (type (RES)) # # loads to convert the string into json format type dict # user_dict = json.loads (RES) # Print (user_dict) # { 'name': ' Tank ',' pwd ':' 123 '} # Print (type (user_dict)) # <class' dict'> # dump # user_info = { # 'name': 'tank', # 'pwd': '123' # } # with open('user_info.json', 'w', encoding='utf-8') as f: # # str1 = json.dumps(user_info) # # f.write(str1) # # dump： 自动触发f.write方法 # json.dump(user_info, f) # load with open('user_info.json', 'r', encoding='utf-8') as f: # res = f.read() # user_dict = json.loads(res) # print(user_dict) # The Load: automatically trigger f.read () user_dict = the json.load (f) Print (user_dict)
4. reptiles
http protocol:
request url:
https://www.baidu.com/
request method:
GET
request header:
Cookie: may need attention.
User-Agent: to prove that you are a browser
NOTE: The browser request headers to find
01 crawling sites
02 crawler pear video
# Requests module # PIP3 the install Requests # PIP3 Tsinghua source address of the install module name -i # PIP3 https://pypi.tuna.tsinghua.edu.cn/simple Requests the install -i # Import Requests # # Response = requests.get ( = URL 'HTTPS: //www.baidu.com/') # response.encoding = 'UTF-. 8' # Print (response) # <the response [200 is]> # # return a response status code # Print (response.status_code) 200 # # # return a response text # # Print (response.text) # Print (type (response.text)) # <class' STR '> # # with Open (' baidu.html ',' W ', encoding ='utf-8') as f: # f.write(response.text) # 爬取梨视频 import requests res = requests.get('https://video.pearvideo.com/mp4/adshort/20190613/cont-1565846-14013215_adpkg-ad_hd.mp4') print(res.content) with open('视频.mp4', 'wb') as f: f.write(res.content)