Post History

> *Assigning the variable end to ']' gets the line number of every closing bracket*

To solve this, just set the last line number **only if** the first line number is already set. Like this:


```python
def readSection(sectionNumber):
    with open(file) as f:
        # before reading the file, first line number is not set
        firstLineNumber = None
        for lineNumber, line in enumerate(f, start=1):
            # start of section found
            if line.startswith(f'[{sectionNumber}'):
                firstLineNumber = lineNumber
            # first line number is set, which means it's the end of the section
            elif firstLineNumber and line[0] == ']':
                lastLineNumber = lineNumber
                break # end of section found, no need to continue the loop
        print(f'first line={firstLineNumber}, last line={lastLineNumber}')
```

With this, if you find a `]` but the first line number is not set yet, it means that it's not the end of the desired section.

And when the end of the section is found, I can interrupt the loop using `break`. There's no need to continue looping, assuming that each section occurs just once in the file.

I've tested with:

```python
readSection(1)
readSection(8)
```

And the output is:

```none
first line=1, last line=3
first line=5, last line=9
```

**PS:** I'm assuming that if a line starts with `]`, it's closing a section. But if there are lines such as `]whatever` and they are part of a session, you should change the code to:

```python
def readSection(sectionNumber):
    with open(file) as f:
        # before reading the file, first line number is not set
        firstLineNumber = None
        for lineNumber, line in enumerate(f, start=1):
            line = line.strip() # remove line break from line
            # start of section found
            if line.startswith(f'[{sectionNumber}'):
                firstLineNumber = lineNumber
            # first line number is set, which means it's the end of the section
            elif firstLineNumber and line.strip() == ']':  # remove line break from line before comparing to ']'
                lastLineNumber = lineNumber
                break
        print(f'first line={firstLineNumber}, last line={lastLineNumber}')
```


---

Note that I can use `enumerate` directly in the file object.

And I didn't use `readlines()` because it will read the whole file and create a list with its contents, and when you loop through it, you're basically looping the file contents twice. For small files it won't make any significant difference, but for big files it may have an impact (but always test to see if it makes some difference).

---
# Return values instead of printing

You could change the function to return the line numbers instead of printing them. By doing this, the code that calls the function decides what to do with the line numbers (print, pass them to another function, etc).

And as said in the comments, the file name could be a parameter of the function, so it becomes more flexible, as it can work with many different files:

```python
def readSection(fileName, sectionNumber):
    with open(fileName) as f:
        # first and last line starts unset
        firstLineNumber = lastLineNumber = None
        for lineNumber, line in enumerate(f, start=1):
            if line.startswith(f'[{sectionNumber}'):
                firstLineNumber = lineNumber
            elif firstLineNumber and line[0] == ']':
                lastLineNumber = lineNumber
                break
        return firstLineNumber, lastLineNumber

first, last = readSection('file.txt', 1)
# check if first or last line is not set
if first is None:
    print('section not found')
elif last is None:
    print('section without closing bracket')
else: # both are set
    print(f'first line number={first}, last line number={last}')
```