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Q&A Python looping 300 000 rows

Based on my last question comes new one. How to loop over 300 000 rows and edit each row string one by one? I have a list of 11-digit numbers stored in one single column in Excel, and I need to s...

1 answer · posted 3y ago by sfrow‭ · last activity 3y ago by NoahTheDuke‭

Question python performance loop

#5: Post edited by

Alexei‭ · 2021-11-10T07:52:17Z (about 3 years ago)
removed non-applicable tag

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python performance loops row

python performance row loop

#4: Post edited by

Alexei‭ · 2021-11-09T06:23:34Z (about 3 years ago)
added relevant tag

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python loops row

python performance loops row

#3: Post edited by

sfrow‭ · 2021-11-08T20:39:29Z (about 3 years ago)

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Based on [my last question](https://software.codidact.com/posts/284803) comes new one.
~~How to loop over 300 000 rows and edit the string one by one?~~
I have a list of 11-digit numbers stored in one single column in Excel, and I need to separate the digits according to this pattern: `2-2-1-3-3`.
I use the code below to loop to test the solution for only 20 rows and it's working.
Example: `00002451018` becomes `00 00 2 451 018`.
`priceListTest` contains the column `Column1` which has these 11 digit numbers. Somehow I need to loop all over these 300 000 rows and use the `get_slices` to change the pattern for each row like from the example above and store it into the new column `New Value`.
The `for index, row` it's working very slowly when I have to use it for 300 000 rows. Maybe there is a better method, but I'm new to python.
Thanks in advance!
```Python
for index, row in priceListTest.iterrows():
#print(index,row)
def get_slices(n, sizes, n_digits=11):
for size in sizes:
n_digits -= size
val, n = divmod(n, 10 ** n_digits)
yield f'{val:0{size}}'
n = row['Column1']
newVar = (' '.join(get_slices(n, [2, 2, 1, 3, 3])))
priceListTest.at[index,['New Value']] = newVar

Based on [my last question](https://software.codidact.com/posts/284803) comes new one.
How to loop over 300 000 rows and edit each row string one by one?
I have a list of 11-digit numbers stored in one single column in Excel, and I need to separate the digits according to this pattern: `2-2-1-3-3`.
I use the code below to loop to test the solution for only 20 rows and it's working.
Example: `00002451018` becomes `00 00 2 451 018`.
`priceListTest` contains the column `Column1` which has these 11 digit numbers. Somehow I need to loop all over these 300 000 rows and use the `get_slices` to change the pattern for each row like from the example above and store it into the new column `New Value`.
The `for index, row` it's working very slowly when I have to use it for 300 000 rows. Maybe there is a better method, but I'm new to python.
Thanks in advance!
```Python
for index, row in priceListTest.iterrows():
#print(index,row)
def get_slices(n, sizes, n_digits=11):
for size in sizes:
n_digits -= size
val, n = divmod(n, 10 ** n_digits)
yield f'{val:0{size}}'
n = row['Column1']
newVar = (' '.join(get_slices(n, [2, 2, 1, 3, 3])))
priceListTest.at[index,['New Value']] = newVar

#2: Post edited by

sfrow‭ · 2021-11-08T20:38:48Z (about 3 years ago)

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~~python looping 300 000 rows~~

Python looping 300 000 rows

#1: Initial revision by

sfrow‭ · 2021-11-08T20:38:30Z (about 3 years ago)

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python looping 300 000 rows

Based on [my last question](https://software.codidact.com/posts/284803) comes new one.<br>
How to loop over 300 000 rows and edit the string one by one?
I have a list of 11-digit numbers stored in one single column in Excel, and I need to separate the digits according to this pattern: `2-2-1-3-3`.<br>
<br>
I use the code below to loop to test the solution for only 20 rows and it's working.<br>
<br>
Example: `00002451018` becomes `00 00 2 451 018`.<br>
<br>
`priceListTest` contains the column `Column1` which has these 11 digit numbers. Somehow I need to loop all over these 300 000 rows and use the `get_slices` to change the pattern for each row like from the example above and store it into the new column `New Value`.<br>

The `for index, row` it's working very slowly when I have to use it for 300 000 rows. Maybe there is a better method, but I'm new to python.<br>
<br>
Thanks in advance!


```Python
for index, row in priceListTest.iterrows(): 
    #print(index,row)
    def get_slices(n, sizes, n_digits=11):
        for size in sizes:
            n_digits -= size
            
            val, n = divmod(n, 10 ** n_digits)
            yield f'{val:0{size}}'

    n = row['Column1']
    newVar = (' '.join(get_slices(n, [2, 2, 1, 3, 3])))
    priceListTest.at[index,['New Value']] = newVar

python loops row

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