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Python

Posted by Shwetha Shyam sunder
Shwetha Shyam sunder
1,369 Points

For those who solved the morse code challenge, can you please explain why we have to use append instead of +=?

When I used pattern1 += 'dot' vs. pattern1.append('dot'), the results were entirely different

class Letter:

def __init__(self, pattern=None):
    self.pattern = pattern

def __str__(self):
    pattern1 = []
    for letter in self.pattern:
        if letter == ".":
            pattern1.append('dot') <<-------- why do we use append here instead of += ?
        elif letter == "_":
            pattern1.append('dash')
        '-'.join(pattern1)
    return '-'.join(pattern1)

1 Answer

markmneimneh
markmneimneh
14,133 Points 
Because pattern1 = []  .... it is an array

You append to an array.   
and you concatenate strings.

if I have an array of strings ....  Example: 
friends = ['Mark', 'Jimmy', 'Albert']
friends.append('Lucus')
print(friends)
# now try to use plus as you are thinking
friends += 'Lucy'
print(friends)

look what happens:

['Mark', 'Jimmy', 'Albert', 'Lucus']   # first print
['Mark', 'Jimmy', 'Albert', 'Lucus', 'L', 'u', 'c', 'y'] #2nd print

Lucy was treated as an array of characters that were added to the friend's arry.

Shwetha Shyam sunder
Shwetha Shyam sunder
1,369 Points

Thank you so much!!!