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pythonnested-loopsnested-lists
NataliaKra
NataliaKra

Reputation: 25

Repeat values in nested list

I am a total newbie and am doing prep work for the bootcamp. I got stuck with the the following Python exercise:

I have a nested list, say, [[1,2],[3,4]]. The first value in each sub-list is the value to repeat, the second is the amount of times to repeat that value.

I want to get a string with numbers repeated appropriate number of times, like "11, 3333". If there are multiple sets of values, they should be separated by commas; if there is only one set the comma should be omitted. I need to create a function.

I tried to create two separate sub-lists for values and number of repetitions, then np.repeat one list by another.

data_list =[[1,2],[3,4]]

num_list = [val [0] for val in data_list]
repeat_list = [val[1] for val in data_list]
result = np.repeat (num_list, repeat_list)

print (result)

[1 1 3 3 3 3]

In this case I do not know how to separate it with commas. And this is not a function.

I feel like I might need to use np.repeat with "for" loop, but I can not figure out exactly how should it look like.

Thanks.

Upvotes: 0

Views: 570

Answers (4)

eroot163pi
eroot163pi

Reputation: 1815

Without for loop and numpy

', '.join(
    map(lambda l: str(l[0])*l[1], data_list)
)

Each entry in list map it to string, then join those strings together

Upvotes: 0

Ram
Ram

Reputation: 4779

You could do like this.

data_list =[[1,2],[3,4]]
res = []
for i in data_list:
    s = str(i[0]) * i[1]
    res.append(s)

print(f'List: {res}')
print(f'String: {", ".join(res)}')

List: ['11', '3333']
String: 11, 3333

Upvotes: 0

BlackMath
BlackMath

Reputation: 1858

A possible solution :

l=  [[1, 2], [3, 4]]

final=[]    
for i in l:
    final.append(list(str(i[0]) * i[1]))

Upvotes: 0

Ben
Ben

Reputation: 480

You could do something like this:

result = ""
for sublist in nested_list:
    # For each sublist, turn the first element into a string, and multiply it by the second element, then add a comma
    result += str(sublist[0]) * sublist[1] + ","

# Remove the last trailing comma
result = result[:-1]

Upvotes: 1

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