Is there a way for Python to detect whether a value is empty?

Question

I'm trying to write a piece of code that will take certain values in a string and output them. The problem is the dataset I'm working with isn't perfect and there are many parts where the data is empty. I'm looking for a way to get python to ignore the blank values and just continue onwards

rfile = open("1.txt", "r", encoding= "utf8")
combos = rfile.readlines()
a=0
nfile = open("2.txt ", "w+")

numx = 0

for line in combos:
    x = combos[a]
    y=(x.split('Points = '))
    z= int(y[-1])
    numx += 1
    print (z)

print (numx)
rfile.close()
nfile.close()
exi = input("Press any key to close")

Example of the dataset would be like:

Person 1 | Points = 22 
Person 2 | Points =     <--- This is the problematic data 
Person 3 | Points = 15

Any help would be greatly appreciated!

Just to clarify, I want python to check whether z is empty, and if it is to just ignore it. — Fast, Jun 21 '20 at 20:09
Does this answer your question? [python: how to check if a line is an empty line](https://stackoverflow.com/questions/7896495/python-how-to-check-if-a-line-is-an-empty-line) — theAlse, Jun 21 '20 at 20:11
More generally, see this answer for what Python considers to be True or False: https://stackoverflow.com/questions/18491777/truth-value-of-a-string-in-python and [the official docs](https://docs.python.org/3/library/stdtypes.html) — , Jun 21 '20 at 20:15
Look at the `y` in the problem line. What is it? string, list, Nine, etc? — hpaulj, Jun 21 '20 at 20:45

score 1 · Answer 1 · answered Jun 21 '20 at 20:11

1

You can check if variable is empty string, or just None, thy something like: if not value: continue

answered Jun 21 '20 at 20:11

Rayan Ral

1,862
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score 0 · Answer 2 · answered Jun 21 '20 at 21:15

After

    y = (x.split('Points = '))

If it is guaranteed that the lines with missing data only have a single space after the =, e.g. 'Person 2 | Points = ' so that y[-1] == '', you can simply do the following to skip over this one and carry on (goes to the start of the next iteration of the for loop):

    if not y:
        continue

relying on the fact that an empty string counts as a false value.

If it might contain additional whitespace, then you will have to deal with this. There are various options:

test the characters of the string one by one

    for c in y[-1]:   # looping over the characters in y[-1]
        if c != ' ':  # if a non-space character is found
            break     # then break from this inner "for" loop
    else:             # but if this loop completed without break
        continue      # then start next iteration of the outer "for" loop

use a regular expression parser (needs import re at the top)

    if re.match('\s*$', y[-1]):
        continue

just try to convert it to int anyway, and catch the exception if it fails:

    try:
        z = int(y[-1])
    except ValueError:
        continue

(All of these will still work if the string is indeed empty.)

Is there a way for Python to detect whether a value is empty?

2 Answers2