(): ... title = "Sir" ... action = (lambda X:title + ' + x) ... return action...>>Gt act = Knight () >>> Act (' Robin ') ' Sir Robin 'In Python 2.2, the value of the variable name title is usually modified to pass in by the value of the default parameter.Why use LambdaIn general, lambda acts as a function sketch, allowing the definition of a function to be embedded within the code used. They are completely optional (you can always use DEF to replace
properties:The properties of the class are categorized all, and all instances of the class have that property.classStudent (object): Name='Student's=Student ()Print(S.name)#StudentPrint(Student.name)#StudentS.name ='Michael' #bind the instance to the Name propertyPrint(S.name)#because instance property precedence is higher than class properties, it masks the name property of the classdelS.name#If you delete the instance's Name propertyPrint(S.name)#call S.name again, because the name property o
two parameters:
The second argument of the Int () function is the conversion, if not passed, the default is decimal (base=10), and if passed, use the passed in parameters.
As you can see, the function's default parameter is to simplify the call , and you just need to pass in the necessary parameters. However, when needed, additional parameters can be passed in to override the default parameter values.
Let's define a function that calculates the n-th square of x:
You ca
to save the result of the last expressionNote: The variable name has no type and the object has3.4 Combined data typesA collection of data elements that are organized in a way, such as numbering an element.Python 's commonly used combination data types Sequence typelist: Using [] create, such as [' call ', ' Me ', ' tshmeal ', '. '] (cannot be changed)tuples: Using () created, such as (' one ', ' one ', ' one ')(can be changed)string also belongs to sequence typedo slice:name = "string"Name[0:
-pip.py -O - |python3#ln -s /opt/apps/python3.5/bin/pip-3.5 /usr/bin/Install required third-party librariessuch as Mysql-connector and requests#pip-3.5 install mysql-connector-python#pip-3.5 install requestsIf the following error occurs when you install PIP:ImportError: No module named bz2This indicates that the installed Python 3 is missing a dependent library b
Python is increasingly favored by "procedural apes". The rapid development model, the Concise code format, the massive expansion, this undoubtedly has laid the foundation for the Python fiery."Ax", a powerful IDE to help developers effectively manage, edit, run engineering code. Python's development IDE compares common Eclipse + Pydev, jetbrains pycharm[charges], and so on, the divine Code editing software
the process of operation, The entire document tree is loaded and then queried for matching operations, consuming more resources in the process and less processing performance relative to XPath
So why use BS4? Because, it, simple enough!
Description Language | handling Efficiency | hands-on level
Regular Expression | Very High Efficiency | Difficult
Xpath | Efficiency is High | Normal
BS4 | High Efficiency | Simple
BS4 itself is a functional operation module that encapsulates the description
print a, B #4, 3
However, there is a problem with variable-length objects, because Python has different effects on variable-length objects and fixed-length objects.
A = [1, 2, 3] B = AA. append (4) print B # B is now [1, 2, 3, 4] as well
What's going on? A declaration statement A = [1, 2,
"," #输出 #alex () {} #后面这个 {} is kwargs, just because there is no value, so it is empty stu_register ("Jack", "+", "CN", "Python", sex= "Male", province= " Shandong ") #输出 # Jack (' CN ', ' Python ') {' province ': ' Shandong ', ' sex ': ' Male '}Local variablesName = "Alex Li" def change_name (name): print ("before change:", name) name = "king of gold horn, a man with tesla" print ("after Chang E ", name)
, and then rewrite the __init__ and run methodsAs with other languages, in order to ensure data consistency between multiple threads, the threading library comes with a lock function, involving 3 interfaces:Thread_lock = Threading. Lock () creates a lock objectThread_lock.acquire () Get lockThread_lock.release () Release lockNote: Because the Python module queue has been implemented multithreaded security,
The most important new feature of Python 3 is probably a clearer distinction between text and binary data. Text is always Unicode, represented by the STR type, and binary data is represented by the bytes type. Python 3 does not mix str and bytes in any implicit way, which makes the distinction between them particularly
element is the same as its tag, this time cannot be positioned through the hierarchy, the index can be positioned as follows:driver.find_element_by_xpath("//select[@id=‘nr‘]/option[1]").click()driver.find_element_by_xpath("//select[@id=‘nr‘]/option[2]").click()driver.find_element_by_xpath("//select[@id=‘nr‘]/option[3]").click()The index here starts at 1, not the same as the Python index.6. XPath Logic oper
‘)print(l)Authorized:Use the instance of the target class to invoke the method of the target class. Equivalent to the method of authorizing the target class with an instance of the target class.1. Add an instance of the target class to the class first2. When you need to invoke a method in the target class, use __getattr__ () to transfer the method of the target class.3, need to modify the target class method, then use the target class instance to give
A string notation 1, a single stringby print() Adding a string to the parentheses, you can output the specified text to the screen. For example ‘hello, world‘ , the output is implemented in code as follows:>>> print(‘hello, world‘)2, multiple stringsprint()A function can also accept multiple strings, separated by a comma "," and can be connected to a string of outputs:>>> print(‘The quick brown fox‘, ‘jumps over‘, ‘the lazy dog‘)The quick brown fox jumps over the lazy dogprint()Each string will
, instead of using elif.
Python while Loop statement
The while statement has two other important commands, Continue,break, to skip the loop, continue to skip the loop, and break to exit the loop.
Looping with Else statements
In Python, for...else means that the statement in for is no different from normal, and the statement in else is executed when the loop is executed normally (that is, for
the parameter, the default value is used inside the function.def Showdefault (a,b=2,c=3): print a,b,cshowdefault (1,4,5) # 1 4 5showdefault (1,4) # 1 4 3showdefault (1) # 1 2 3Binding ParametersWhen defining a function, you can use *args to specify that the parameter is accessed as a tuple in the function, using **args to specify that the parameter is used in dictionary formdef Showargs (*args): print argsshowargs (1,2,3,4
list dict str Although it is iterable iterator the list,dict,str and other iterable into Iterator You can use the iter () function:Example:iter ([]) iterator Python iterator object represents a data flow, Iterator next () function calls and returns the next data continuously until no data is thrown stopiteration error. You can think of this data stream as an ordered sequence, but we can't know the length of the sequence in ad
1, solve the user input blank line method using Startwith judgment or Len (STRs) >02. Strip and replace are particularly useful in the use of string methods.The Python Strip () method removes the character specified by the string's Kinsoku (the default is a space). Grammar:Str. Strip([chars]);#!/usr/bin/pythonstr = "0000000this is string EXAMPLE....WOW!!! 0000000 ";p rint Str.strip (' 0 '); #输出结果为this is string EXAMPLE....WOW!!!Removes only the chara
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