Python Fabric not able to find substring in string

Question

I have 2 lists of identical length. One contains the substrings I want to find, one contains the longer string in which I am trying to find the substring (it will always be at the beginning of the line). The lists I have contain one entry where the substring is not in the string; the second entry has the substring in the string.

However, it looks like python can't figure out when the substring is there or not. I've tried a lot of different ways.

if substring in string
if string.find(substring) != -1
if string.startswith(substring) != -1

The first two "if" statements above always return false. The last "if" statement always returns true.

def agentID():
index = 1
while index < 3:
    ID = linecache.getline('/home/me/project/ID', index)
    agentLine = linecache.getline('/home/me/project/agentIDoutput', index)
    str(agentLine)
    if agentLine.startswith('%s' % str(ID)) != -1:
        print("%s: Proper Agent ID %s found in client.keys" % (env.host_string, ID))
        index = index + 1
    else:
        print("I couldn't find %s in the line %s" % (ID, agentLine))
        index = index + 1

This seems pretty simple and straightforward. I even tried explicitly converting to strings to ensure I was searching on the same type. That's what I'm thinking my error is, but it seems to interpret them both as strings.

add print(repr(ID), repr(agentLine)) before the compare to see what strings you are comparing. And as mentioned below, don't compare for -1. if agentLine.startswith(ID) should suffice. — tdelaney
– tdelaney, Commented Mar 20, 2016 at 16:03
FYI: .getline() obviously already returns a string (otherwise you'd encounter TypeErrors), so you don't need to convert it. But if you did need to, you'd have to use agentline = str(agentline) - you need to reassign the result of str(). — Tim Pietzcker
– Tim Pietzcker, Commented Mar 20, 2016 at 16:03
You'll find that the lines have "\n" in them. Do ID.strip() to get a better compare. — tdelaney
– tdelaney, Commented Mar 20, 2016 at 16:05

Tim Pietzcker · Accepted Answer · 2016-03-20 16:00:30Z

0

string.startswith() returns either True or False which are de facto the integer values 1 and 0, respectively.

Therefore, if string.startswith(substring) != -1 will always be True.

Apparently, your substring simply isn't present in your string.

answered Mar 20, 2016 at 16:00

Tim Pietzcker

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1 Comment

Carl_Friedrich_Gauss Over a year ago

I have no idea because what you indicated worked! thank you!

tdelaney · Accepted Answer · 2016-03-20 16:12:08Z

0

print is your friend. I tried a quick test:

>>> import linecache
>>> print(repr(linecache.getline('tmp/testfile.txt', 1)))
'line 1\n'

linecache gives you the full line including newline. Just strip it off of the end. You had a couple of other problems I cleaned up while I was here

def agentID():
    for index in range(1,4):
        ID = linecache.getline('/home/me/project/ID', index).strip()
        agentLine = linecache.getline('/home/me/project/agentIDoutput', index)
        if agentLine.startswith(ID):
            print("%s: Proper Agent ID %s found in client.keys" % (env.host_string, ID))
        else:
            print("I couldn't find %s in the line %s" % (ID, agentLine))

answered Mar 20, 2016 at 16:12

tdelaney

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Carl_Friedrich_Gauss Over a year ago

Thanks. I took out the newline and changing correcting the "startswith" was my problem. I read about the "find" method and assuming the values returned (i.e. -1 for false) were the same for the "startwith" method.

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