Built-in functions 1

exec and eval

exec and evak can perform a string type of code
evak only be used in code that you know exactly what you want to do is
eval has a return value, - for the outcome of a simple calculation
exec did not return. - suitable for simple process control

Exec ( ' Print (123) ' ) 
the eval ( ' Print (123) ' )
 Print (the eval ( ' . 1 + 2 +. 3 +. 4 ' )) # return a value 
Print ( Exec ( ' . 1 + 2 +. 3 +. 4 ' )) # no return value

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For example exec

#应用exec
code = '''for i in range(8):
        print('*'*i)'''
exec(code)

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complie

String code is compiled, the object code that can be executed or be evaluated through the eval exec statement.

compile () Usage
'' 'the compile (parameters: ast and string or object' code file name: the file when reading the code from the inside, otherwise empty ', implementation: eval or Exec)' ''

code1 = '1+2+3'
h = compile(code1,'','eval')
print(eval(h))

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Note that when an interactive, need to exec mode to single line.