Author: John Au-Yeung

Sometimes, we want to execute a program or call a system command with Python.

In this article, we’ll look at how to execute a program or call a system command with Python.

How to execute a program or call a system command with Python?

To execute a program or call a system command with Python, we can use the subprocess.run method.

For instance, we write:

import subprocess
subprocess.run(["ls", "-l"])

We pass in an array with the command as the first entry.

And the options are in the subsequent entries.

Now we should see the listings of the content of the current working directory displayed.

Conclusion

To execute a program or call a system command with Python, we can use the subprocess.run method.

Sometimes, we want to merge two dictionaries in a single expression with Python.

In this article, we’ll look at how to merge two dictionaries in a single expression with Python.

How to merge two dictionaries in a single expression with Python?

To merge two dictionaries in a single expression with Python, we can use the ** or | operators.

For instance, we write:

x = {'a': 1, 'b': 2}
y = {'b': 3, 'c': 4}
z = {**x, **y}
print(z)

Then z is {'a': 1, 'b': 3, 'c': 4}.

** is available since Python 3.5.

We can also use the | operator with Python 3.9 or later.

To use it, we write:

x = {'a': 1, 'b': 2}
y = {'b': 3, 'c': 4}
z = x | y

And we get the same value for z.

Conclusion

To merge two dictionaries in a single expression with Python, we can use the ** or | operators.

Sometimes, we want to check whether a file exists without exceptions with Python.

In this article, we’ll look at how to check whether a file exists without exceptions with Python.

How to check whether a file exists without exceptions with Python?

To check whether a file exists without exceptions with Python, we can use the os.path.isFile method.

For instance, we write:

import os.path
fname = './foo.txt'
os.path.isfile(fname) 

fname is a file path string.

If the file doesn’t exist at the fname path, then it returns False.

Conclusion

To check whether a file exists without exceptions with Python, we can use the os.path.isFile method.

Sometimes, we want to add a ternary conditional expression with Python.

In this article, we’ll look at how to add a ternary conditional expression with Python.

How to add a ternary conditional expression with Python?

To add a ternary conditional expression with Python, we can following the following format:

a if condition else b

where a and b are expressions.

For instance, if we have:

'true' if True else 'false'

Then true is returned.

Conclusion

To add a ternary conditional expression with Python, we can following the following format:

a if condition else b