在python内部时从命令行执行Python多行语句

Question

I've got thousands of small multi-line python3 programs to run, which are generated as strings. They all have a similar structure, and end with a print command. Here's some simple examples

prog_1 = 'h=9\nh=h+6\nprint(h)'
prog_2 = 'h=8\nh-=2\nprint(h)'
prog_3 = 'c=7\nc=c+4\nprint(c)'

They should all be executable if you were to run them from the interpreter. What I mean is, they look like small normal programs when you print them,

>>> print(prog_1)
h=9
h=h+6
print(h)


>>> print(prog_2)
h=8
h-=2
print(h)


>>> print(prog_3)
c=7
c=c+4
print(c)

I want to execute them from inside my program, (which generates them), and capture the output, (ie the output of the print ) as a variable, but I'm stuck how to do it?

Something like

import os
output = os.popen("python -c " +  prog_1).read()

would be great but I get this error?

/bin/sh: 3: Syntax error: word unexpected (expecting ")")

I think the problem is I don't know how to execute the small programs from the command line? This line executes, but does not print out??

python -c "'h=9\nh=h+6\nprint(h)'"

Thanks a lot for your help :)

Answer 1

If you are not bound to command line you can use:

exec(prog_1)

Warning : exec() can be very dangerous - Why should exec() and eval() be avoided?

Answer 2

You can use exec :

>>> prog_1 = 'h=9\nh=h+6\nprint(h)'
>>> exec(prog_1)
15

Answer 3

If you wish to execute them in a separate process then you can use subprocess.run :

>>> prog_1 = 'h=9\nh=h+6\nprint(h)'
>>> result = subprocess.run(["python"], input=prog_1, encoding="utf-8", stdout=subprocess.PIPE).stdout
>>> print(result)
15

Note that Python 3.6 is required for encoding support, and Python 3.5 is required for subprocess.run .

In Python 3.5, you need to pass the input as bytes , and the returned output will also be bytes.

>>> result = subprocess.run(["python"], input=bytes(prog_1, "utf-8"), stdout=subprocess.PIPE).stdout
>>> print(str(result, "utf-8"))
15