key value can be int; like String,array, Dictionary is also a value copy7.Set7.1) Declare the set with Set7.2) Set also has a for in traversal, there are two sets of the difference between the way to do the arrangement, but also a subset of the judgment of the method of the superset8.For Cycle8.1) for the index in 1...5 this index is only within the scope of the current loop, and if there is an index outside the for loop, any modification will not affect it.8.2) For _ in 1...10 if you do not ne
source file in the macro definition, data structure type definition, static variables, static function declaration, function implementation.11, the essence of the function is 3 big program structure--order structure, cycle structure, select structure, these kinds of structure mix constitute the procedure.12. Array of string pointer constants13, external variables in the header file with an extern representation declaration (declaration, cannot be initialized), in the source file defined variabl
information they have lost. At this point, the browser will display this alternative text instead of the image. It is a good practice to add alternate text attributes to the images on the page, which helps to better display the information and is useful for those who use a plain text browser. Basic considerations-Helpful tips: If an HTML file contains 10 images, you need to load 11 files in order to display the page correctly. Loading pictures takes time, so our advice is: Use images with cauti
are signed numbers2. Floating-point value, if not specified, the default is double type3. When defining float type, be sure to indicate float type, which can be expressed by adding "F" or "F" after the number.4. Char represents a 16-bit unsigned (non-positive) Unicode character, and a char character must be enclosed in single quotation marks.5. There is no conversion calculation between the integer type and the Boolean type. You cannot convert integer types and logical types directly in Javastr
constantsSecond, operatorArithmetic Operators+ 、-、 *,/,% (remainder operation can only be used for integer type)Relational Operators> >= == !=logical Operators! | | (the expression whose connection is evaluated from left to right, and stops the calculation immediately after knowing that the result value is False or True )bitwise operators (only for integer operands) (to be continued ...) )~ | ^ Type Conversions (when several operand types of an operator are different, they need to be converte
, output vectorsSeq ()# arithmetic progressionSTR ()# Each property of the data frameSummary ()# Calculates basic statistics for all columnsTable ()# computed column tableTapply () # function operations on all subsetsUnique ()# Find tick valueVector ()# spawn Vectors# environment and loading, output dataRead.table ()# Read Data fileScan ()# Read Data fileSETWD ()# Set Current working directoryWrite.table ()# output file# drawingJPEG ()# open JPG imagePlot ()# Scatter chartDev.off ()# Close pictu
Description 1.switch is clearer and more readable than if...else statements 2.python does not provide a switch statement
3.pthon uses a dictionary to implement the switch statement function, the implementation method is divided into 2 steps:A. Define a dictionary;B. Call the dictionary get () to get the corresponding expressionPython code:
def add(x,y):
return x+y
def sub(x,y):
return x-y
def mul(x,y):
return x*y
def div(x,y):
return x/y
operation={
1. Statements are executed on a line-by-row basis, unless you do not writeIf the statement uses an if statement, his execution is jumping, and the IF statement is the process control2. Automatic boundary detection of blocks and statementsBecause Python does not have curly braces for these bounding symbols, it uses code indentation to control boundariesSimilarly, the end of a statement is not using semicolons, but also using code indentationIn the above example, for the indentation before the for
role: This function is mainly for the purpose of serialization objects. Maybe some people are allergic to the word serialization, my understanding is very simple. This means converting the type of the object to a string type (or, more specifically, the JSON type). It's so simple. For example, you have a class, so you can convert it to the corresponding JSON type by this method. It's simple.Then look.Syntax:Json.stringify (value [, Replacer] [, space])Value: is the required field. Is the object y
add a withxxx,xxx is the first parameter infix)Then I must declare this: Func Processdata2withparamaa (paramaa:string,paramab:string) {}Crouching trough, what a ghost!!And then call it? There is a wood in the outside of the brackets. There's no sense of paramaa inside. Processdata2withparamaa ("a""b")The OC call function is like this [self processdatawithparamaa:@ "A" paramab:@ "B"]Both sides are in brackets.This elegance your swift braces don't learn.Fortunately, the development of t
the Python standard library.1) Network application based on socket layerSockets are the bottom line of the Network Programmability section. With the socket package, we can manage the socket directly, such as assigning a socket to a port, connecting a remote port, and transferring data over a connection. We can also use the Socketserver package to build servers more easily. With multi-threaded and multi-process coordination, the establishment of multi-threaded or multi-process server, can effect
1 //input A, B, output a+b2 /*#include 3 int main ()4 {5 int A, b;6 scanf ("%d%d", a,b);7 printf ("%d", a+b);8 }*/9 /*Ten //Enter a character to return his ASCLL code One #include A int main () - { - char A; the scanf ("%c", a); - printf ("%d", a); - }*/ - + -#include + intMain () A { at CharA; - Charb; - while(scanf ("%c%c", a,b)!=eof)//when there is a space in the middle, the input parameters should also have a space, when there is no space, you do not have to enter a space.
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