A very simple read n lines implementation, available in all natural, classic and generator flavors.

readnlines.py

def readnlines(filehandler, n=4):
    line_groups = []
    while True:
        nlines = []
        for i in range(n):
            line = filehandler.readline()
            if line:
                nlines.append(line.strip())
            else:
                if nlines:
                  line_groups.append(nlines)
                return line_groups
        else:
            line_groups.append(nlines)

def xreadnlines(filehandler, n=4):
    line_cache = []
    for line in filehandler:
        line_cache.append(line.strip())
        if len(line_cache) == n:
            yield line_cache
            line_cache = []
    else:
        yield line_cache