Python alternative to bash head command: prints the first -n lines of a text file defined within the string.

magic_head.py

from IPython.core.magic import register_line_magic
from itertools import islice


@register_line_magic
def head(parameter_s=''):
    '''Prints the first -n lines of a text file defined within the string.
	Examples:
	%head -n 5 file.txt
	%head -5 file.txt
  
  This file has to be placed in the startup subdirectory of your default IPython profile
  e.g. 'user\.ipython\profile_default\startup'
	'''
    if not parameter_s:
        raise Exception('Missing filename')
        
    list_parameters = parameter_s.split()
    assert len(list_parameters) <= 3, "Inappropriate command: use '%head -n 5 file.txt' or '%head -5 file.txt'"   
    
    filename = list_parameters[-1]
    
    if len(list_parameters)==1:
        N = 5
    elif len(list_parameters)==2 and list_parameters[0][0] == "-":
        try:
            N = abs(int(list_parameters[0]))
        except UsageError:
            print("Inappropriate command: use '%head -n 5 file.txt' or '%head -5 file.txt'")
            return
    elif len(list_parameters)==3 and list_parameters[0] == "-n":
        try:
            N = abs(int(list_parameters[1]))
        except UsageError:
            print("Inappropriate command: use '%head -n 5 file.txt' or '%head -5 file.txt'")
            return
    else:
        raise Exception("Inappropriate command: use '%head -n 5 file.txt' or '%head -5 file.txt'")
        
    try :
        with open(filename) as file:
            for line in islice(file, N):
                print(line)
    except (ValueError, IOError):
        print(filename+"?")
        print("Error: no such file, variable, URL, history range or macro")
        return

# In an interactive session, we need to delete these to avoid
# name conflicts for automagic to work on line magics.
del head

Add
#!/usr/local/bin python3
the the top of the file.
I'm also getting an error,
zsh: permission denied: magic_head