Python Notes

Python

Syntax

• from ... import ... as ...
  import 的后面内容对本模块可见
  package1.package2.module.name

  只要import涉及到package，该package下的__init__.py 会被自动执行

  package is a folder, containing many python files and __init__.py

  module.py is a python file in the package

  name is a finc,var,class of module.py

  from package.package import module
  from package.package import module.name
  from package.package.module import name
  from . import module   # `.` 代表当前模块的目录， 入口模块中 `.` 代表 __main__
  from .package import module
  

  绝对导入的参照物是入口模块，相对导入的参照物是当前模块

  在Python2.6前默认为相对导入，之后默认为绝对导入

• Library install

  # 在线安装，在CMD窗口中运行
  easy_install pandas
  pip install pandas  # pip是easy_install的改进版
  
  # whl文件离线安装，在CMD窗口运行
  pip install xxxxx.whl
  
  # 压缩包离线安装，在CMD窗口运行
  python setup.py install 
  

Annex A. Syntax Summary

	C/C++	Python	Matlab
Create	int a[3] = {}	a = [1,2,3]	a = [1,2,3]
Index	a[0]	a[0]	a(1)
IndexFrom	0	0	1
Row/Col	[][first]	[][first]	(first, )
if-else	else if	elif	elseif
Relation Operator	==, !=, >=	==, !=, >=	==, ~=, >=
Logical Operator	&&, ||, !	and, or, not	&&, ||, ~
Logical Operator (element-wise)	-	-	&, |, ~
Bit Operator	&, |, ^, ~, <<, >>	&, |, ^, ~, <<, >>	bitand,bitor,bitxor,bitnot,bitshift
Power	pow(a, b)	a ** b	a ^ b
Rem	a % b	a % b	rem(a,b)
numpy.array		A.ndim	ndims(A)
		A.shape	size(A)
		A.size	numel(A)
		A * B	A .* B
		A @ B	A * B

Syntax

Note that in Python, x[(exp1, exp2, ..., expN)] is equivalent to x[exp1, exp2, ..., expN]; the latter is just syntactic sugar for the former.
https://numpy.org/doc/stable/user/basics.indexing.html

jupyter notebook

安装：pip install notebook
运行：jupyter-notebook pytorch
使用国内镜像库 -i https://pypi.tuna.tsinghua.edu.cn/simple

Python教材

Think Python - How to Think Like a Computer Scientist 2nd
Python Cookbook - David Beazley
Fluent Python - Luciano Ramalho
Effective Python