Locating index of item via REGEX in Python

Question

I've hit a wall and need some help.

Context: I have a list of lists of strings.

 Matrix = [['444'],
          ['23%'],
          ['A']]

For the moment, we have a list of Counts at position 0, Percentage at 1 and Significance test at 2.

The number of lists within the list changes from 3 to 2 to 1 from time to time. And the type of string within the list changes position. So I cannot assume that index 0 will always be Counts and percentage will be 1 etc.

Hence I wanted to find a way of dynamically finding out where percentage, for example, is located in the Matrix, and if its even in there.

Here is what I've written so far:

for i, row in enumerate(Matrix):
    for cell in row:
        if "%" in cell:
            percent = i
            print percent
for i, row in enumerate(Matrix):
    for cell in row:            
        if re.search('[a-zA-Z]', cell):
            sigtest = i
            print sigtest
for i, row in enumerate(Matrix):
    for cell in row:
        if re.search('[0-9]', cell):
            count = i
            print count

Output:

Problem: As you can see, the problem is located with the last for loop which records the fact that index 0 and 1 contain numbers.

Whats needed: A way for the last for loop to search for numbers and numbers only, a item contains numbers and a symbol, that index should not be included.

Hope that makes sense!

thanks

Ashwini Chaudhary · Accepted Answer · 2013-07-23 11:43:34Z

1

To check whether the string contains only digits you can use :

>>> bool(re.search(r'^[0-9]+$', '4444'))
True
>>> '4444'.isdigit()    #Doesn't work for floats
True
# This will work for floats as well
>>> bool(re.search(r'^[0-9]*(\.[0-9]+)?$', '4444.123'))
True
>>> bool(re.search(r'^[0-9]*(\.[0-9]+)?$', '.123'))
True

For percentage you can use this regex

>>> bool(re.search(r'^[0-9]+%$', '23%'))
True
#To handle floats as well use this:
>>> bool(re.search(r'^[0-9]*(\.[0-9]+)?%$', '23.15%'))
True
>>> bool(re.search(r'^[0-9]*(\.[0-9]+)?%$', '.150%'))
True

For sigtest:

>>> bool(re.search(r'^[a-z]$', 'a',re.I))
True
>>> bool(re.search(r'^[a-z]$', 'B',re.I))
True

Here ^ and $ are meta-characters:

^ matches the start of the string and $ matches the end of the string.

answered Jul 23, 2013 at 11:43

Ashwini Chaudhary

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4 Comments

elnabo Over a year ago

You only match unsigned number. You may start with (-|+)?.

Boosted_d16 Over a year ago

@ Ashwini, thanks for that. I tested it and the problem remains. If I want to find the index of a percentage string in the list (Matrix), your code will give me index 0 & 1 instead of 1 alone. I guess its because index 0 contains numbers too. Ideally, I want to run a single function to get the index of count, percent and significance.

Ashwini Chaudhary Over a year ago

@Boosted_d16 No it won't, for '444' my regex will return False. bool(re.search(r'^[0-9]+%$', '444')) --> False. You're doing something wrong.

Boosted_d16 Over a year ago

@Ashwini, your correct. I dont know what I was doing wrong before but yes, it works. Thanks again!

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