Python implementation of the program in two ways
Interactive (eg: jupyter)
Pros: Run an implementation of a
Disadvantages: Close disappear
Command-line (eg: pycharm)
Pros: has been saved
Disadvantages: all finished before they can debug bug
Although txt file can run, but try to use py file
Later try to use pycharm or jupyter
Code farmers (only grammar, without thinking (hands-on experience / own summary), project experience (summary bug))
each encounter a bug, recorded (is not it a look)
What are the variables: Description of changes in the state of things in the world
Height: 160, weight: 140
"""
height = 160
print(height) # 160（变量值）
"""
weight = 140
print (weight) # 140 (variable value)
weight = weight + 1
print(weight) # 141
Compositional variables
Variable name (variable value received) = (assignment symbol) variable value (value) is defined variable #
Naming the variable name
Height = 180 # is not recommended, but may do so
print (height)
weight = 160
name = 'nick'
1. Variable names must consist of number / letter / underscore _ Composition
height_of_nick = 180 # underlined only when connected with
2. Variable names are readable (sense) deposit is not an end, is the purpose of taking
3. Do not use keywords as variable names (characters that have a special meaning)
'''
['and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec',
'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print',
'raise', 'return', 'try', 'while', 'with', 'yield']
'''
Both definitions way a variable name
height_of_nick = 180 # underlined formula (convention)
Print (height_of_nick)
Heightofnick = 180 # hump body (very low, such as (C / the JAVA))
Print (heightofnick)
Constant: the same amount, nature is a constant variable, but the variable name in all capital convention constants, not to change the constants
age = 18 #变量
Age = Age Tasu 1
Print (Age)
AGE = 18 # So all uppercase letters is constant
AGE = AGE + 1
print(AGE)
Variable memory management (frequently asked interview)
##: description of the state of all things worldly
height = 180 # define a variable
print (180) # print will automatically help you create a variable 180, later printed, immediately release the memory space 180
The reference count is defined
# Define a variable, the memory will open up a memory space to store the variable
# reference count (for variable value)
# reference count is 0, touch
# send garbage collection mechanism, release the memory occupied
The definition of small integers pool
Since the [#] -5,256 used more, [- 5,256] is automatically opened when the python interpreter to start, so they are not affected by garbage collection mechanism for jupyter
### Note: pycharm in optimized , a short interval of time, no matter how big, id are the same
GIL Global Interpreter Lock
Three variables defined characteristic values
height = 180 # variable name (descriptive)
# fetch values of the memory address for the value of the variable
Print (ID (height))
# data types, variable values for
print (type (height)) # int type (integer type)
= name 'Nick'
Print (type (name)) # STR type (string string)
Fancy assignment
height_of_nick = 180
height_of_handsome = 160
heigh_of_yongjiu = 170
print(height_of_nick)
print(height_of_handsome)
print (heigh_of_yongjiu)
Cross assignment (decompression)
height_of_nick,height_of_handsome,heigh_of_yongjiu=180,160,170
print(height_of_nick)
print(height_of_handsome)
print(heigh_of_yongjiu)
Modify the x and y at the same address how to ensure cases
x = 2000
print ( 'x:' id (x))
y = 1000
print ( 'y:' id (y))
Thinking of intermediate variables
# z = x
# x = y
# y = z
Cross assignment
X, Y = Y, X
Print ( 'Y:', ID (Y)) # same memory address, the same value must
print ( 'x', id ( x))
x = 1000
y = 2000
print ( 'y', id ( y)) # same value, the memory address is not the same
print ( 'x', id ( x))
Chain assignment (the same value to use)
# # a = 10
# b = 10
# c = 10
# print(a,b,c)
a=b=c=10
print(a,b,c)
Note
# Single-line comments
# Interpretation; let code to run when the python interpreter not to be interpreted, that let him senseless
# a = 10
# print(a)
Picasso picasso_height = 160 # height, interpreted code means
# Explained above code into code block
Print # 0-9
for i in range(10):
print(i)# Ctrl + / (comment shortcuts)
Multi-line comments #
'' '
A = 10
Print (A)
' ''