Author: John Au-Yeung

Sometimes, we want to remove all packages installed by pip with Python.

In this article, we’ll look at how to remove all packages installed by pip with Python.

How to remove all packages installed by pip with Python?

To remove all packages installed by pip with Python, we run pip uninstall.

To use it, we run

pip freeze | xargs pip uninstall -y

to run pip freeze to get the list of packages installed.

And then we pipe that to xargs pip uninstall -y to remove all the packages listed by pip freeze with pip uninstall.

We use the -y to remove everything without needing confirmation.

Conclusion

To remove all packages installed by pip with Python, we run pip uninstall.

Sometimes, we want to print multiple arguments in Python.

In this article, we’ll look at how to print multiple arguments in Python.

How to print multiple arguments in Python?

To print multiple arguments in Python, we can print f-strings.

For instance, we write

print(f'Total score for {name} is {score}')

to call print with a f-string that interpolates the values of name and score into the string.

This works since Python 3.6.

Conclusion

To print multiple arguments in Python, we can print f-strings.

Sometimes, we want to make Python tkinter label widget update.

In this article, we’ll look at how to make Python tkinter label widget update.

How to make Python tkinter label widget update?

To make Python tkinter label widget update, we assign the textvariable argument a StringVar object before we call set to update the label.

For instance, we write

v = StringVar()
Label(master, textvariable=v).pack()

v.set("New Text!")

to create a label with

v = StringVar()
Label(master, textvariable=v).pack()

We set textvariable to a StringVar object to make set update the label.

Then we call set to update the label to display ‘New Text!’.

Conclusion

To make Python tkinter label widget update, we assign the textvariable argument a StringVar object before we call set to update the label.

Sometimes, we want to fix appending turns my list to NoneType with Python.

In this article, we’ll look at how to fix appending turns my list to NoneType with Python.

How to fix appending turns my list to NoneType with Python?

To fix appending turns my list to NoneType with Python, we shouldn’t assign the return result append to the list.

For instance, instead of writing

a_list = ['a', 'b', 'c', 'd']  
a_list = a_list.append('e')  

We write

a_list = ['a', 'b', 'c', 'd']  
a_list.append('e')  

since append appends 'e' to a_list in place and returns nothing.

Conclusion

To fix appending turns my list to NoneType with Python, we shouldn’t assign the return result append to the list.

Sometimes, we want to know if a generator is empty from the start with Python.

In this article, we’ll look at how to know if a generator is empty from the start with Python.

How to know if a generator is empty from the start with Python?

To know if a generator is empty from the start with Python, we can call next to see if the StopIteration exception is raised.

For instance, we write

def peek(iterable):
    try:
        first = next(iterable)
    except StopIteration:
        return None
    return first, itertools.chain([first], iterable)

res = peek(my_sequence)
if res is None:
    # ...
else:
    # ...

to define the peek function.

In it, we call next with iterable to see if the first item is returned or the StopIteration exception is raised.

If the error is raised, we return None.

Otherwise, we return first and the iterator that we get by calling chain with [first] and iterable which no longer has the first object.

Then we call peek to see is the returned result is None to see if the generator is empty.

Conclusion

To know if a generator is empty from the start with Python, we can call next to see if the StopIteration exception is raised.