How to check if an application is open in Python?

A process is a program under execution. When an application runs on your operating system, it creates one or more processes. Python provides several methods to check if a specific application is currently running on your system.

We'll explore three different approaches to check if an application is open: using the psutil module, the subprocess module, and the wmi module for Windows systems.

Using psutil.process_iter() Function

The psutil module provides a cross-platform interface for retrieving information about running processes and system utilization. It works on Linux, Windows, macOS, Solaris, and AIX.

First, install psutil using ?

pip install psutil

Example Checking if Chrome is Running

Here's how to check if a specific process is currently running ?

import psutil

def check_if_process_running(process_name):
    for process in psutil.process_iter(['name']):
        if process.info['name'] == process_name:
            return True
    return False

# Check if Chrome is running
result = check_if_process_running("chrome.exe")
print(f"Is Chrome running? {result}")

Is Chrome running? False

Example Getting Detailed Process Information

You can also retrieve detailed information about all running processes ?

import psutil

# Get first 5 processes for demonstration
processes = list(psutil.process_iter())[:5]
for process in processes:
    try:
        print(f"Process: {process.name()} | PID: {process.pid}")
    except (psutil.NoSuchProcess, psutil.AccessDenied):
        pass

# System information
cpu_percent = psutil.cpu_percent()
memory_usage = psutil.virtual_memory()

print(f"\nCPU usage: {cpu_percent}%")
print(f"Memory usage: {memory_usage.percent}%")

Process: python.exe | PID: 1234
Process: notepad.exe | PID: 5678
Process: explorer.exe | PID: 9012
Process: svchost.exe | PID: 3456
Process: chrome.exe | PID: 7890

CPU usage: 10.6%
Memory usage: 51.9%

Using subprocess Module

The subprocess module allows you to execute system commands from Python. On Windows, you can use the tasklist command to check running processes.

Example

This method uses Windows' built-in tasklist command ?

import subprocess

def is_process_running(process_name):
    cmd = 'tasklist /fi "imagename eq {}"'.format(process_name)
    output = subprocess.check_output(cmd, shell=True).decode()
    if process_name.lower() in output.lower():
        return True
    else:
        return False

result = is_process_running("notepad.exe")
print(f"Is Notepad running? {result}")

Is Notepad running? True

Using wmi Module (Windows Only)

Windows Management Instrumentation (WMI) is a Windows-specific tool for managing local and remote computers. The wmi module provides Python access to WMI functionality.

Install the wmi module ?

pip install wmi

Example

Here's how to use WMI to list running processes ?

import wmi

f = wmi.WMI()
print("PID   Process Name")
print("-" * 25)

# Show first 10 processes for demonstration
count = 0
for process in f.Win32_Process():
    if count < 10:
        print(f"{process.ProcessId:<5} {process.Name}")
        count += 1
    else:
        break

PID   Process Name
-------------------------
0     System Idle Process
4     System
124   Registry
524   smss.exe
752   csrss.exe
868   csrss.exe
888   wininit.exe
940   services.exe
960   lsass.exe
320   winlogon.exe

Comparison

Conclusion

Use psutil for cross-platform process checking with detailed information. For Windows-only applications, subprocess with tasklist or wmi module provide native OS integration. The psutil approach is recommended for most use cases due to its portability and rich feature set.