Python Full Stack development * 02 Knowledge Point Summary * 180531

operators and encodings

One formatted output

1. Enter name, age, job, hobby.

Output:---------------info of Mary------------------

Name:mary

Age:18

Job:teacher

Hobbie:sing

----------------------End-------------------------

Eg:name = input ("Name:")

Age = Input ("Age:")

Job = Inut ("Job:")

Hobby = input ("HOBBT:")

info = ""

----------------------------Info of%s---------------# Each%s is a placeholder, (name)

Name:%s #代表name

Age:%s #代表 age

Job:%s #代表 Job

Hobby:%s #代表 Hobbie

--------------------------------End----------------------

'% (name,name,age,job,hobbie) # This is the line that associates the preceding string with the variable following the parentheses

Print (info)

2.%s,%d

%s represents a string placeholder; Everything can be converted directly to a string, only "%s".)

%d represents a digit placeholder. (Only numbers can be entered, and the corresponding data must be of type int).

3. Data type conversions:

int (str) # string converted to int

STR (int) # int converted to string

4. "Percent" to indicate "%" in the string.

If a placeholder such as%s is used in a string, all% will become placeholders, so "%" in the string is required to represent "percent"

Note: If you do not use%s,%d placeholder in the string, you do not need to use it instead.

Eg:print ("My name is%s, I'm 22 years old, I learned 2% of python"% ' Mary ') # has% placeholder.

Print ("My name is Mary, I'm 22 years old, I've finished my Homework 100%") # no placeholder

Two basic operators

1. Arithmetic operations "plus", "minus", "multiply", "except", "modulus (take Out) [%]", "power [*]", "divisible [//] ".

The% modulo returns the remainder of the division a=10, B=20, then the result of the b%a output is 0;

* * Power to return a to the power of B a=10, b=20, then A**b is 10 of the 20-th square;

Take the integer portion of the returned quotient a=10, b=20, then 9//2 output result 4, 9.0//2.0 output result 4.0.

2. Comparison Operations

= = Equals (compares objects are equal); # a "=" is an assignment

! = does not equal (compares two objects are not equal);

<> does not equal (compares two objects are not equal);

> Greater than

< less than (all operators return 1 for True ==>true, 0 for false ==>false);

>= greater than or equal to

<= less than or equal to

3. Assignment operation (Set a = ten, b =20)

= Simple assignment operator c=a+b indicates that the result of the a+b operation is assigned to C;

+ = Addition Assignment operator C+=a is equivalent to C=c+a;

The-= Subtraction assignment operator c-=a is equivalent to c=c-a;

The *= multiplication assignment operator c*=a is equivalent to c=c*a;

The/= Division assignment operator C/=a is equivalent to c=c/a;

The%=-to-film assignment operator C% A is equivalent to c=c% A;

The **= power assignment operator C **= A is equivalent to C=C * * A;

= The integer-divisible assignment operator C//=a is equivalent to c=c//a.

4. Logical operation

and Boolean "and" if a is false, A and B returns false, otherwise it returns the calculated value of "B" ;

or boolean "or" if a is true, a or B returns true, otherwise it returns the calculated value of "B ";

Not Boolean "non" if a is true, not a returns Falseif a is flase, it returns TRUE.

Attention:

1. In the absence of () the not priority is higher than and, and the and priority is higher than or,

That is, the priority relationship is () > Not > and >or . The same priority is computed from left to right).

2. x or Y, X is True, value is True, X is False, value is y;

X and Y,x are true, the value is Y, X is false, and the value is x;

3. Not false is neither true nor false.

Three-coding problem

1. Interpreter

The PYTHON2 interpreter encodes the content with "ASCII";

The PYTHON3 interpreter encodes the content with "UTF-8".

2. Development of the coding system

ASCII    (US standard Information Interchange code) 8 bit 1 byte extended use limited;

GBK              (GBK compatible ASCII) 2 byte in China only

eg: letter a:0100 0001 # ASCII

Letter a:0000 0000 0100 0001 # GBK GB Code

Unicode                           (Universal Code) 4 byte wasted

UTF-8 (variable length) English 8 bit 1 byte

Chinese bit 3 byte

3. Unit conversions

8 bit = 1 byte

1024x768 byte = 1KB

1024x768 KB = 1MB

1024x768 MB = 1GB

1024x768 GB = 1TB

1024x768 TB = 1PB

......

Python Full Stack development * 02 Knowledge Point Summary * 180531