Use 1.pycharm shortcuts
ctrl + c copy, copy the entire row default
ctrl + v to paste
ctrl + z revocation
ctrl + x shear, shear default entire row
ctrl + a select all
crtl + f to find, select Batch Edit
shift + ctrl + z trans revocation
ctrl + d copy and paste the selected content, the entire row is not selected by default
ctrl + backspace to delete a word
ctrl + y delete the entire line
ctrl + w to select a word
shift + enter wrap
ctrl + shift + r global search
shift + f10 to run on a file
ctrl + shift + f10 to run the current file
ctrl + alt + l formatting code
ctrl + / overall comments
home back to the beginning of the line
end back end of line
2. Variable
variable
All things change in the definition of state
Compositional variables
Variable name (to be described, to accept the value of the variable) of assignments (assignments, the value of the variable pass variable names) values (specific values)
Variable naming specification
Named variables should reflect the state variable values expressed in, remember not to use Chinese
Variable names must underscore combination of alphanumeric, and the first character variable names can not be digital
Keywords can not be declared as a variable name
Two options for defining variables
Hump body
Underline style
3. Constant
Amount does not change (constant names all uppercase), no constant is change convention, in fact, may vary.
4.python Memory Management
Defined variables and running will open up a new memory space to store variable
Reference count (whole team variable value): value of the variable reference number
Garbage collection: reference count of zero when a variable value, triggers the garbage collection mechanism, the variable value will be recovered
Small integer pool: When Python starts, it will automatically define an integer variable between [-5,256], it will not be garbage collection mechanism
The three print form variable
age=10
#打印值
print(age)
#打印内存地址
print(id(age))
#打印数据类型
print(type(age))6. What is the data type
Data types of variable values made a classification of different categories
Integer float string boolean value dictionary list
7. Digital Type
Integer (int)
1. Role
It represents the person's age, all kinds of numbers, level
2. Definitions
age=18
age=int(18)3. Use
x = 1
y = 2
print(x + y)
print(x - y)
print(x * y)
print(x / y)
print(x % y) # 取余
print(x // y) # 取整
print(x ** y) # 幂Float (float)
1. Role
He represents height, weight, payroll
2. Definitions
salary=3.2
salary=float(3.2)3. Use
+ - * / % // **8. String
1. Role
He represents the name of hobbies
2. Definitions
name='nick'
int_str=str(123)3. Use
Self string comparison logic + *
9. Comment
Single-line comments '' ''
Multi-line comments '' '' ''