Python进阶-pickle/eval/exec

Posted 2020-12-26 下划线是我

• 参考:
  • 　　eval/exec/compile的区别：https://stackoverflow.com/questions/2220699/whats-the-difference-between-eval-exec-and-compile-in-python
  • 　　pickle的使用: https://pythontips.com/2013/08/02/what-is-pickle-in-python/
• 背景
  • 之前用打印到文件，逐行读出用eval转换格式。现在用pickle可直接实现。
• pickle_eval_exec的区别:
  • pickle: dump到file, 从file中load
  • eval: eval accepts only a single expression， eval returns the value of the given expression。
  • exec: exec can take a code block that has Python statements: loops, try: except:, class and function/method definitions and so on. return None.
• Pickle的使用:(pickle.load(), pickle.dump())

import pickle

a = [‘test value‘,‘test value 2‘,‘test value 3‘]
a
[‘test value‘,‘test value 2‘,‘test value 3‘]

file_Name = "testfile"
# open the file for writing
fileObject = open(file_Name,‘wb‘) 

# this writes the object a to the
# file named ‘testfile‘
pickle.dump(a,fileObject)   

# here we close the fileObject
fileObject.close()
# we open the file for reading
fileObject = open(file_Name,‘r‘)  
# load the object from the file into var b
b = pickle.load(fileObject)  
b
[‘test value‘,‘test value 2‘,‘test value 3‘]
a==b
True