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The code object contains not only the bytecode but also some other information necessary for the CPython to run the bytecode (they will be discussed later). c = compile("a=a+1", "", "single") type(c) # Output is: code In a similar way, the bytecode generated by the compile function is stored in the code object. For example we you define an integer variable, its value is stored in an int object and you can easily check its type using the type() function: a = 5 type(a) # Output is: int The compile() function returns a Python code object. So what the compile function is returning is a code object (the address after at can be different on your machine). However, we can use the single mode to compile it: compile("a=a+1", "", "single")īut what is returned by compile? When you run the compile function, Python returns: at 0x000001A1DED95540, file "", line 1> Here a=a+1 is not an expression and does not return anything, so we cannot use the eval mode. This mode gives an error if you don’t have an expression: # This does not work: compile("a=a+1", "", "eval") To evaluate an expression we can write: compile("a+7", "", "eval") Or equivalently write: compile("a=5 \na+=1 \nprint(a)", "", "exec") If the last statement is an expression, then the resulting bytecode prints the repr() of the value of that expression to the standard output.įor example, to compile some Python statements we can write: s=''' a=5 a+=1 print(a) ''' compile(s, "", "exec") 'single': only accepts a single statement (or multiple statements separated by ).
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'eval' : accepts a single expression and compiles it into a bytecode that finally returns the value of that expression It compiles them into a bytecode that finally returns None 'exec': accepts Python source code in any form (any number of statements or blocks). If the source code does not come from a file, you can write whatever you like or leave an empty string.
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filename is the name of the file that the source code comes from. source is the source code to compile which can be a String, a Bytes object, or an AST object. We only focus on the first three arguments which are required (the others are optional). The syntax of this function is:Ĭompile( source, filename, mode, flag, dont_inherit, optimize) We can also use the compile() function to compile a string that contains the Python source code. If you provide no file names after compileall, it will compile all the python source code files in the current folder. file_n.pyĪll the generated pyc files will be stored in the _pycache_ folder. To compile the individual files file_1.py to file_n.py from the command line, we can write: python -m compileall file_1.py. In that case, we can still manually create it. However, it will not be created if we don’t import another file in the source code. This folder is automatically created when you try to import another file that you created: import file_name
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In Python 3, the bytecode files are stored in a folder named _pycache_. CPython compiles the python source code into the bytecode, and this bytecode is then executed by the CPython virtual machine. The default implementation of the Python programming language is CPython which is written in the C programming language. The bytecode is platform-independent, but PVM is specific to the target machine. The PVM is an interpreter that runs the bytecode and is part of the Python system. In fact, it is a set of instructions for a virtual machine which is called the Python Virtual Machine (PVM).Īfter compilation, the bytecode is sent for execution to the PVM. The bytecode is a low-level platform-independent representation of your source code, however, it is not the binary machine code and cannot be run by the target machine directly. py extension), Python first compiles it into a bytecode. When we execute a source code (a file with a. Python is usually called an interpreted language, however, it combines compiling and interpreting. The interpreter, which is specific to the target machine, translates each statement of the source code into machine code and runs it. There is another program called the interpreter that reads and executes the source code directly. In an interpreted language, the source code is not directly run by the target machine. After compilation, the target machine will directly run the machine code. This machine code is specific to that target machine since each machine can have a different operating system and hardware. In a compiled language, a compiler will translate the source code directly into binary machine code. The source code of a programming language can be executed using an interpreter or a compiler.