# How to separate strings in a list, multiplied by a number

## Question:

I need to take a list, multiply every item by 4 and separate them by coma.

My code is:

``````conc = ['0.05 ml : 25 ml', '0.05 ml : 37.5 ml', '0.05 ml : 50 ml', '0.05 ml : 62.5 ml', '0.05 ml : 75 ml']
new_conc = [", ".join(i*4) for i in conc]
print(new_conc)
``````

But when I run it, I get every SYMBOL separated by come. What I need is multiplied number of shown EXPRESSIONS separated by coma.

So the output should be:

`['0.05 ml : 25 ml', '0.05 ml : 25 ml', '0.05 ml : 25 ml', '0.05 ml : 25 ml', '0.05 ml : 37.5 ml', '0.05 ml : 37.5 ml', '0.05 ml : 37.5 ml', '0.05 ml : 37.5 ml', '0.05 ml : 50 ml', '0.05 ml : 50 ml', '0.05 ml : 50 ml', '0.05 ml : 50 ml', '0.05 ml : 62.5 ml', '0.05 ml : 62.5 ml', '0.05 ml : 62.5 ml', '0.05 ml : 62.5 ml', '0.05 ml : 75 ml', '0.05 ml : 75 ml', '0.05 ml : 75 ml', '0.05 ml : 75 ml']`

I found this answered question, but as I already mentioned, I get separate symbols, separated by coma.

You can try double for-loop:

``````conc = ['0.05 ml : 25 ml', '0.05 ml : 37.5 ml', '0.05 ml : 50 ml', '0.05 ml : 62.5 ml', '0.05 ml : 75 ml']

out = []
for item in conc:
for _ in range(4):
out.append(item)
print(out)
``````

Or one-liner:

``````out = [item for item in conc for _ in range(4)]
``````

Or (if order as you stated in your output is not important):

``````out = conc * 4
``````

Okay, when I despaired of finding an answer and posted this question, I found this answered question. ðŸ™‚

So the solution to my problem can be:

``````b = [4, 4, 4, 4]
c = sum([[s] * n for s, n in zip(conc, b)], [])
print(c)
``````

But, if you, guys, know better solution, I will be happy to hear it!

You can use a simple `for` loop.

``````new_conc = []
for item in conc:
new_conc.extend([item] * 4)
``````

Welcome to StackOverFlow! As correctly pointed out by other users, you can’t directly multiply a string, you need to "separate" the numeric part from the non-numeric one, then you can perform your multiplication, and finally rejoin the numeric and the string parts.

``````conc = ['0.05 ml : 25 ml', '0.05 ml : 37.5 ml', '0.05 ml : 50 ml', '0.05 ml : 62.5 ml', '0.05 ml : 75 ml']

multiplied_conc = [': '.join([f"{float(p.split()[0])*4} {p.split()[1]}" for p in c.split(' : ')]) for c in conc]

print(multiplied_conc)
``````
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