Search and Replace a text string from text file using python 3.5

Question

Badly need assistance on this:

f = open('/Volumes/Personal/example.text','r+')

for line in f:
    print(line, end='')
    if (line.startswith("path = ")) in f:
        line = CurrentFilePath + "\n" 
        f.write(line)
        print ("Success!!!!")
    else:
        print('Errorrrr!!!')

this line of code just reads the file, and as soon as the line which needs to be read and then replaced, it throws an error! Please help. Very very new to python.

why the `in f` in the if statement? is this the error you are getting? — Francesco, Apr 13 '16 at 12:25
I dont get error, it reads the that text file. But, when the line to be read is the one which I'm expecting to be replaced, it goes to else block! — Vighnesh Pai, Apr 13 '16 at 12:26
I'm not getting my program executed at if (line.startswith("path=") in f — Vighnesh Pai, Apr 13 '16 at 12:28

score 2 · Accepted Answer · answered Apr 13 '16 at 12:30

2

Your problem is in your if statement:

if (line.startswith("path = ")) in f:

When you reach a line that start with "path = ", that line evaluates to:

if True in f:

...which doesn't really make sense. Files don't contain boolean values. Simply removing the in f will get you past that; it's not doing anything for you here.

answered Apr 13 '16 at 12:30

glibdud

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OKay.. Great. That worked, can you do me a favour now? The string is not being replaced, can you help me with that? – Vighnesh Pai Apr 13 '16 at 12:32
@VighneshPai Sounds like that should be a new question. – glibdud Apr 13 '16 at 12:33
@VighneshPai Why would you assume that it will be replaced, if you are never *replacing* it in the code? – C Panda Apr 13 '16 at 12:34
@glibdud Please help dude, I'm really struck here.! – Vighnesh Pai Apr 13 '16 at 12:34
I just wanted to point out that `True in f` always returns `False`. This is why only the else block is hit – Francesco Apr 13 '16 at 12:34
@CPanda I'm replacing entire line! – Vighnesh Pai Apr 13 '16 at 12:35
@VighneshPai where exactly? – C Panda Apr 13 '16 at 12:35
@VighneshPai You might want to search for "python replace text in file". There have been a number of questions on that subject. – glibdud Apr 13 '16 at 12:35
@glibdud please help here http://stackoverflow.com/questions/36598728/replace-entire-line-in-a-text-file-based-on-search-using-python – Vighnesh Pai Apr 13 '16 at 12:41

score 0 · Answer 2 · answered Apr 13 '16 at 12:32

0

f is an iterator and in operator in for loop is made to call next() on it. What is in doing with if? Check the syntax for if. Delete in f from that line and hopefully it will work.

answered Apr 13 '16 at 12:32

C Panda

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Search and Replace a text string from text file using python 3.5

2 Answers2