Knowledge -python data type 1

table of Contents

1. Description of garbage collection
2. Reference counting exercise
3. Description of small integers pool concept
4. For x = 10, respectively, please use python code print variable values, variable values ​​and the variable data memory type
5. For the following codes:

x = 257
y = x
z = 257

Please judge x, y, z values ​​of the variables are the same? x, y, z where the memory address is the same? Please elaborate why the python code?

1. Digital Type Description
2. Description string type

text

1. Brief Python garbage collection:
   • Reference count: references to the objects the counter is 0, automatically reclaims the memory
   • Clear labeling: fast trigger memory overflow, clear a specific variable names. Resolve the circular reference problem
   • Generational Recovery: Depending on the median survival time is divided into different levels, the lower, the higher the level garbage collection sweep frequency
2. For the following codes:

x = 10
y = 10
z = 10
del y

10 reference count of how many?

Reference count 2

x = 257
y = x
del x
z = 257

Corresponding to the variable x 257 reference count of how many?

Reference count 2

1. Brief Python small integer pool concept:

   Python implementation int time there is a small integer pool. In order to avoid creating the same value repeated application memory space efficiency brought about by the range [-5,256], small integer objects within that range is to be reused within the scope of the global interpreter, will never be garbage collection recycling.

2. For x = 10, with Python code print variable values, respectively, the memory address of the variable value and the variable data types:

x = 10

print(x)
print(id(x))
print(type(x))

1. For the following codes:

x = 257
y = x
z = 257

Please judge x, y, z values ​​of the variables are the same? x, y, z where the memory address is the same? Please elaborate why the python code?

The same value

Pycharm the same memory address, different in cmd

a1 = print(x)
b1 = print(y)
c1 = print(z)
a1 = b1 = c1

a2 = print(id(x))
b2 = print（id(y)）
c2 = print(id(z))
a2 =! b2
a2 =! c2
b2 =! c2

1. Digital Type Description

   • Integer

     Role: that age, number, etc.

     Defined way

     x = 1
     x = int(1)

   • Float

     Role: represents the height, weight, etc.

     Defined way

     x = 1.0
     x = flout(1)

2. Description string type

   Role: table name, gender, appearance, etc.

   Defined method:

   String is a string of the character string to string together, in a single or double wrapped string of characters triple quotes

name = 'bigb'
sex = "male"
hobby = '''
sing
dance
rap
basketball
'''