Getting the integer value from a list of strings

Question

I have a string list which looks like this:

Loops = ['Loop 0 from point number 0 to 965', 
         'Loop 1 from point number 966 to 1969',
         'Loop 2 from point number 1970 to 2961']

I am trying to get the range of the point numbers from the above list of strings.

For example: LoopStart1 = 0, LoopEnd1 = 965, LoopStart2 = 966, LoopEnd2 = 1969

I can imagine using for loops or string slicing to do that but how exactly / which commands should I use to specifically take the point numbers (integers) from these list of strings? Since the numbers each have different lengths.

Thanks in advance!

Answer 1

You can use regex to do it. Then create a dictionary to store all values:

import re

Loops = ['Loop 0 from point number 0 to 965', 
         'Loop 1 from point number 966 to 1969',
         'Loop 2 from point number 1970 to 2961']
d = {}
for index, value in enumerate(Loops):
    m = re.findall(r'\d+ to \d+', value) 
    m = [i.split('to') for i in m]
    d[f'LoopStart{index+1}'] = int(m[0][0])
    d[f'LoopEnd{index+1}'] = int(m[0][-1])

print(d)

Output:

{'LoopStart1': 0, 'LoopEnd1': 965, 'LoopStart2': 966, 'LoopEnd2': 1969, 'LoopStart3': 1970, 'LoopEnd3': 2961}

Explanation:

This line gets the index and item of that loop. i.e. index = 0,1,2... and value = 'Loop 0 from...', 'Loop 1 from ....'

for index, value in enumerate(Loops):

This line finds all the strings which start with a number, have 'to' in between, and end with a number.

m = re.findall(r'\d+ to \d+', value) 

This line splits the m string by to.

m = [i.split('to') for i in m]

This line adds the loop item with starting value in a dictionary called d

d[f'LoopStart{index+1}'] = int(m[0][0])

This line adds the loop item with an ending value in a dictionary called d

d[f'LoopEnd{index+1}'] = int(m[0][-1])

Also, this f'{value}' of creating strings is called f-strings.

Answer 2

You can use a nested list comprehension:

pl=[f'LoopStart{ln+1} = {ls}, LoopEnd{ln+1} = {le}' 
        for ln, ls, le in [[int(w) for w in line.split() if w.isnumeric()] 
            for line in Loops]]


>>> print(', '.join(pl))
LoopStart1 = 0, LoopEnd1 = 965, LoopStart2 = 966, LoopEnd2 = 1969, LoopStart3 = 1970, LoopEnd3 = 2961

Breaking that down, this part makes sub lists of the numbers found:

>>> sl=[[int(w) for w in line.split() if w.isnumeric()] 
...                     for line in Loops]
>>> sl
[[0, 0, 965], [1, 966, 1969], [2, 1970, 2961]]

Then this part makes a list of formatted strings from the values in those sublists:

>>> pl=[f'LoopStart{ln+1} = {ls}, LoopEnd{ln+1} = {le}' for ln, ls, le in sl]
>>> pl
['LoopStart1 = 0, LoopEnd1 = 965', 'LoopStart2 = 966, LoopEnd2 = 1969', 'LoopStart3 = 1970, LoopEnd3 = 2961']

Then join together:

>>> ', '.join(pl)
'LoopStart1 = 0, LoopEnd1 = 965, LoopStart2 = 966, LoopEnd2 = 1969, LoopStart3 = 1970, LoopEnd3 = 2961'