Python内置函数(60)——compile
英文文档:
compile
(source, filename, mode, flags=0, dont_inherit=False, optimize=-1)
- Compile the source into a code or AST object. Code objects can be executed by
exec()
oreval()
. source can either be a normal string, a byte string, or an AST object. Refer to theast
module documentation for information on how to work with AST objects. - The filename argument should give the file from which the code was read; pass some recognizable value if it wasn’t read from a file (
'<string>'
is commonly used). - The mode argument specifies what kind of code must be compiled; it can be
'exec'
if source consists of a sequence of statements,'eval'
if it consists of a single expression, or'single'
if it consists of a single interactive statement (in the latter case, expression statements that evaluate to something other thanNone
will be printed). - The optional arguments flags and dont_inherit control which future statements (see compile(). If the flags argument is given and dont_inherit is not (or is zero) then the future statements specified by the flags argument are used in addition to those that would be used anyway. If dont_inherit is a non-zero integer then the flags argument is it – the future statements in effect around the call to compile are ignored.
- __future__ module.
- The argument optimize specifies the optimization level of the compiler; the default value of
-1
selects the optimization level of the interpreter as given by-O
options. Explicit levels are0
(no optimization;__debug__
is true),1
(asserts are removed,__debug__
is false) or2
(docstrings are removed too). - This function raises
SyntaxError
if the compiled source is invalid, andValueError
if the source contains null bytes. - If you want to parse Python code into its AST representation, see
ast.parse()
. - Note: When compiling a string with multi-line code in
'single'
or'eval'
mode, input must be terminated by at least one newline character. This is to facilitate detection of incomplete and complete statements in thecode
module. - Changed in version 3.2: Allowed use of Windows and Mac newlines. Also input in
'exec'
mode does not have to end in a newline anymore. Added the optimize parameter. - Changed in version 3.5: Previously,
TypeError
was raised when null bytes were encountered in source. - 将字符串编码成代码或者AST对象,使之能通过 exec 语句来执行或者 eval 来取值
- 说明:
- 1. 将source编译为代码或者AST对象。代码对象能够通过exec语句来执行或者eval()进行求值。
- 2. 参数source:字符串或者AST(Abstract Syntax Trees)对象。即需要动态执行的代码段。
- 3. 参数 filename:代码文件名称,如果不是从文件读取代码则传递一些可辨认的值。当传入了source参数时,filename参数传入空字符即可。
- 4. 参数mode:指定编译代码的种类,可以指定为 ‘exec’,’eval’,’single’。当source中包含流程语句时,mode应指定为‘exec’;当source中只包含一个简单的求值表达式,mode应指定为‘eval’;当source中包含了交互式命令语句,mode应指定为'single'。
>>> #流程语句使用exec >>> code1 = 'for i in range(0,10): print (i)' >>> compile1 = compile(code1,'','exec') >>> exec (compile1) 0 1 2 3 4 5 6 7 8 9 >>> #简单求值表达式用eval >>> code2 = '1 + 2 + 3 + 4' >>> compile2 = compile(code2,'','eval') >>> eval(compile2) 10 >>> #交互语句用single >>> code3 = 'name = input("please input your name:")' >>> compile3 = compile(code3,'','single') >>> name #执行前name变量不存在 Traceback (most recent call last): File "<pyshell#29>", line 1, in <module> name NameError: name 'name' is not defined >>> exec(compile3) #执行时显示交互命令,提示输入 please input your name:'pythoner' >>> name #执行后name变量有值 "'pythoner'"