Python: Lambda expression

Question

I'm trying to take input as:

1.jpg 10.png 11.png 2.jpg 3.png

and print out to a list by using lambda expression:

['001.jpg', '010.png', '011.png', '002.jpg', '003.png']

files = input().split()

print(list(map('{0:03d}.{1}'.format(lambda x: int(x.split('.')[0]), x.split('.')[1], files))))

I thought I did it right. But it occurs an error as: AttributeError: 'list' object has no attribute 'split'

What am I missing?

@hpaulj AttributeError: 'list' object has no attribute 'split' — peaberry
– peaberry, Commented Oct 26, 2019 at 4:16
You can split a string into a list of strings. Make sure you understand what each variable is. — hpaulj
– hpaulj, Commented Oct 26, 2019 at 4:27
I'm not able to get your error. My error indicates that passing a lambda function as an argument to format is not allowed. The answer given by @Ofer Sadan is very elegant, you should use it. Since you want to know what you missed I sugest to look at this way of doing it print (list (map(lambda x : '{0:03d}.{1}'.format(int(x.split('.')[0]), x.split('.')[1]), files) )) — Gabriel Avendaño
– Gabriel Avendaño, Commented Oct 26, 2019 at 4:43

Ofer Sadan · Accepted Answer · 2019-10-26 04:23:20Z

3

You don't need any map or lambda, just zfill:

print([x.zfill(8) for x in input().split()])

Adjust 8 in this example to whatever length you need

answered Oct 26, 2019 at 4:23

Ofer Sadan

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1 Comment

Didn't even think of zfill nice answer!

Ajax1234 · Accepted Answer · 2019-10-26 04:15:28Z

2

You can use simple str.split and calculate the padding from the length of the digit as a string:

s = '1.jpg 10.png 11.png 2.jpg 3.png'
result = list(map(lambda x:'0'*(3-len(x.split('.')[0]))+x, s.split()))

Output:

['001.jpg', '010.png', '011.png', '002.jpg', '003.png']

answered Oct 26, 2019 at 4:15

Ajax1234

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Can you help me out on my code as well? I just want to know what I'm missing

Jab · Accepted Answer · 2019-10-26 04:21:26Z

1

A list comprehension is more efficient here than map and lambda and way more readable.

s = '1.jpg 10.png 11.png 2.jpg 3.png'
result = ['{0:0>3}.{1}'.format(*x.split('.')) for x in s.split()]

answered Oct 26, 2019 at 4:21

Jab

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