subprocess.run() is a recommended method for running external commands in Python, which is safer and more powerful than os.system. 1. Basic usage: Use a list to pass commands and parameters, such as subprocess.run(['ls', '-l'], capture_output=True, text=True), and the return result contains the return code, standard output and error. 2. Use shell to execute complex commands: support shell features such as pipelines through shell=True, such as subprocess.run('echo "hello" | grep "hello"', shell=True, capture_output=True, text=True), but it should be avoided for user input to prevent injection risks. 3. Check the command successfully: Set check=True to throw a CalledProcessError exception when the command fails, which is convenient for error handling. 4. Pass environment variables: Pass into the custom environment through the env parameter, such as copying os.environ and adding new variables. 5. Real-time output: subprocess.run() does not support real-time output by default. Capture_output can be omitted and output directly to the terminal, or use subprocess.Popen to implement streaming reading instead. 6. Common parameters include args, shell, capture_output, text, check, timeout, cwd and env. Reasonable combination can meet the needs of most scenarios. It is recommended to use list-form commands to improve security, and finally complete external command calls in a concise and safe way.
subprocess.run() is a common method used in Python to run external commands. It belongs to the subprocess module and is recommended to use it since Python 3.5. It is more powerful and safer than old methods such as os.system or subprocess.call , and supports rich parameter configuration.
Below are some practical subprocess.run() examples to help you get started quickly.
? Basic usage: Run simple commands
import subprocess
# Run the ls command (Linux/macOS) or dir (Windows)
result = subprocess.run(['ls', '-l'], capture_output=True, text=True)
print("Return code:", result.returncode)
print("Output:", result.stdout)
print("Error:", result.stderr)Notice:
- Commands and parameters are passed in a list form to avoid the risk of shell injection.
capture_output=Truecaptures standard output and standard errors.text=Trueconverts the output from bytes to string.
? Use shell to execute complex commands (such as with pipes)
import subprocess
result = subprocess.run(
'echo "hello world" | grep "hello"',
shell=True,
capture_output=True,
text=True
)
print("Output:", result.stdout)?? Note:
shell=Truehas security risks, do not use it on user input.
? Check whether the command is successful (exception is automatically thrown)
import subprocess
Try:
result = subprocess.run(
['python', '--version'],
check=True, # Throw CalledProcessError when failure
capture_output=True,
text=True
)
print("Success:", result.stdout)
except subprocess.CalledProcessError as e:
print("Command execution failed, return code:", e.returncode)? Pass environment variables
import subprocess
import os
custom_env = os.environ.copy()
custom_env["MY_VAR"] = "hello"
result = subprocess.run(
['python', '-c', 'import os; print(os.getenv("MY_VAR"))'],
env=custom_env,
capture_output=True,
text=True
)
print("Environment variable output:", result.stdout)? Real-time output (not recommended to use run, use Popen instead)
subprocess.run() is to wait for the command to end before returning, which is not suitable for real-time output. If you need real-time printout, you should use subprocess.Popen .
But if you still want to use run and print the output, you can do this:
import subprocess # Do not capture the output, print directly to the terminal subprocess.run(['echo', 'Hello, World!'])
Or output while executing (requires to close capture):
subprocess.run(['ls', '-l'], text=True) # The output will be printed directly
? Common parameters summary
| parameter | illustrate |
|---|---|
args
|
Commands and parameters (lists or strings) |
shell=True
|
Execute using shell interpreter (use with caution) |
capture_output=True
|
Capture stdout and stderr |
text=True
|
Output as a string instead of bytes |
check=True
|
When the return code is not 0, the exception is thrown |
timeout=10
|
Timeout setting (seconds) |
cwd='/path'
|
Specify the working directory |
env=...
|
Custom environment variables |
Basically these common scenarios. For most script tasks, subprocess.run() is sufficient with capture_output=True and text=True , which is safe and concise.
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