Python字典值修改失效求助：alien_3的x_position未正确更新

Hey there! Let's break down why your code isn't giving the updated x-position you expect—it's a tiny, easy-to-miss typo that's throwing everything off.

The Core Issue: Misspelled Dictionary Key #

Look at the line where you try to update the alien's position:

alien_3['x_postion'] = alien_3['x_position'] + x_increment

You accidentally spelled x_position as x_postion (missing an 's' between 't' and 'i').

Since dictionaries rely on exact key names, this line doesn't modify the original 'x_position' key in your dictionary. Instead, it creates a brand new key called 'x_postion' that holds the updated value.

Then, when you print the result:

print('New x_postion : ' + str(alien_3['x_position']))

You're still referencing the original 'x_position' key (which never got updated), so it outputs the initial value of 0.

Fixed Code #

Here's the corrected version with the typos fixed:

alien_3 = {'x_position' : 0, 'y_position' : 25, 'speed' : 'medium'}
print ('Original x_position: ' + str(alien_3['x_position']))
# Move the alien to the right
# Determine how far to move the alien based on its current speed
if alien_3['speed'] == 'slow':
    x_increment = 1
elif alien_3['speed'] == 'medium':
    x_increment = 2
else:
    # This alien must be really fast
    x_increment = 3
# The new position is the old position plus the increment
alien_3['x_position'] = alien_3['x_position'] + x_increment
print('New x_position : ' + str(alien_3['x_position']))

What It Does Now #

When you run this corrected code, you'll see:

Original x_position: 0
New x_position : 2

Which matches the medium speed increment of 2 that you defined.

内容的提问来源于stack exchange，提问作者Tim De Combe