在打开文件函数的一段长字符串中切片

Question

Hi everyone I am new to StackOverflow,

I am trying to make a slice of every line in a .dat file that I have been given.

The purpose is for an event study where I am supposed to open the file and then manipulate the data when the file is opened using '.readlines' it is a giant string with numbers. There are when printing the usual '\\n' to indicate a new line.

What I have been given is the character length of integer values for each column name to eventually create a dataframe. This is what I am trying to slice over.

In total there are 73 characters for one line. From this line 20 characters at the start are for the adjusted close price of shares then the next 17 charactes are the share high price etc etc. I am trying to get this slice of 20 characters and then 17 character that are after the 20 and then so on.

I feel that the first step is to convert the file into into a list which I have done through '.readlines' (still unsure if this is the right way) and then iterate through each element in the list slicing.

The file through '.readlines' looks like this:

'00041.1501808166503954.22999954223633053.61999893188476600000072014-08-14\\n', '0040.92996978759765654.590000152587890054.3400001525878900000102014-08-15\\n', '0041.24130249023437554.520000457763670054.3899993896484400000072014-08-18\\n',

What I am trying to get is a seperate list for the first 20 characters for each new line. So for the above it will be something like this:

list = [00041.15018081665039, 0040.929969787597656, 0041.241302490234375 .....]

It is not meant to be complicated code either, but any suggestions are really appreciated!

Thanks a lot

Answer 1

Basic list comprehension should do the trick:

Try this code:

lines = ['00041.1501808166503954.22999954223633053.61999893188476600000072014-08-14\n', 
         '0040.92996978759765654.590000152587890054.3400001525878900000102014-08-15\n', 
         '0041.24130249023437554.520000457763670054.3899993896484400000072014-08-18\n']
         
blocks = [ln[:20] for ln in lines]

print(blocks)

Output

['00041.15018081665039', '0040.929969787597656', '0041.241302490234375']