简单的python IF语句不起作用？

Question

In my code, I am trying to check a specific line of a config file by using linecache to read the line and an if statement to see if it is True, but for some reason it refuses to work.

I simplified the code in order to test it.

import linecache

d = linecache.getline('logconfig.dat', 2)

print(d)
if d == True:
    doeslock = True
else:
    doeslock = False

print(doeslock)

No matter what I try, print(d) will print True , and print(doeslock) will print False . I even tried using letters and strings instead of bools. Still didnt work. What am I missing here?

Thanks in advance guys

EDIT:

When I used strings to do the comparison, I replaced the True in the file with ay and modified the if statement to see if the d variable is 'y'

EDIT 2:

Ok guys I found the problem. Turns out the linecache returned both the line I want and the previous one for whatever reason. I separated the config into two files and now it works fine. No idea what caused this to happen but oh well. Thanks for the help!

Answer 1

When you read a line from a file, you get the whole line, including the newline character, as a string. You should strip that off and then compare with another string:

if d.strip('\n') == "True":

Answer 2

The string is not the same as the boolean value. Consider:

>>> d = 'True'
>>> print(d)
True
>>> if d == True:
...   doeslock = True
... else:
...   doeslock = False
... 
>>> print(doeslock)
False
>>> bool('False')
True

What you probably want is:

import linecache

d = (linecache.getline('logconfig.dat', 2)).strip()

print(d)
doeslock = (d == 'True')

print(doeslock)

Also consider the following:

>>> with open('randfile', 'w') as whatever:
...   whatever.write('y')
... 
>>> import linecache
>>> d = linecache.getline('randfile', 1)
>>> print(d)
y

>>> d == 'y'
False
>>> 'y' in d
True
>>> d.strip() == 'y'
True

Answer 3

linecache.getline returns a string, not a boolean. So you have to compare d to "True" . You also may have to strip the result of getline in case there are spaces or newline.

>>> if d=="True":
...   print 'ok'
...
ok

Answer 4

尝试d.strip（）=='True'：可能是您有多余的空间或\\ n。

Answer 5

import linecache

d = linecache.getline('logconfig.dat', 2)

print(d)

if d:

doeslock = True

else:

doeslock = False

print(doeslock)