Confusing error when trying to run Python script

Question

I'm trying to run this simple Python code (a.py):

# list test
import time
class List(object):
  class Cons(object):
    def __init__(self, x, tail):
      self.x= x
      self.tail=tail
  class Nil(object):
    def __init__(self):
      pass
  @classmethod
  def cons(cls, cons):
    return List(cons, None)
  @classmethod
  def nil(cls, nil):
    return List(None, nil)
  def __init__(self, cons, nil):
    self.cons = cons
    self.nil = nil

def replicate(n, x):
  return List.nil(List.Nil()) if n == 0  else List.cons(List.Cons(x,replicate(n-1,x)))

t1 = time.time()
List.cons(List.Cons(object(), List.nil(List.Nil())))
t2 = time.time() - t1
print t2

But it's not working:

$ ./a.py 
Version: ImageMagick 6.8.8-10 Q16 x86_64 2014-04-08 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2014 ImageMagick Studio LLC
Features: DPC Modules OpenMP
Delegates: bzlib djvu ltdl png zlib

Usage: import [options ...] [ file ]

Image Settings:
  -adjoin              join images into a single multi-image file
  -border              include window border in the output image
  -channel type        apply option to select image channels
  -colorspace type     alternate image colorspace
  -comment string      annotate image with comment
  -compress type       type of pixel compression when writing the image
  -define format:option
                       define one or more image format options
  -density geometry    horizontal and vertical density of the image
  -depth value         image depth
  -descend             obtain image by descending window hierarchy
  -display server      X server to contact
  -dispose method      layer disposal method
  -dither method       apply error diffusion to image
  -delay value         display the next image after pausing
  -encipher filename   convert plain pixels to cipher pixels
  -endian type         endianness (MSB or LSB) of the image
  -encoding type       text encoding type
  -filter type         use this filter when resizing an image
  -format "string"     output formatted image characteristics
  -frame               include window manager frame
  -gravity direction   which direction to gravitate towards
  -identify            identify the format and characteristics of the image
  -interlace type      None, Line, Plane, or Partition
  -interpolate method  pixel color interpolation method
  -label string        assign a label to an image
  -limit type value    Area, Disk, Map, or Memory resource limit
  -monitor             monitor progress
  -page geometry       size and location of an image canvas
  -pause seconds       seconds delay between snapshots
  -pointsize value     font point size
  -quality value       JPEG/MIFF/PNG compression level
  -quiet               suppress all warning messages
  -regard-warnings     pay attention to warning messages
  -respect-parentheses settings remain in effect until parenthesis boundary
  -sampling-factor geometry
                       horizontal and vertical sampling factor
  -scene value         image scene number
  -screen              select image from root window
  -seed value          seed a new sequence of pseudo-random numbers
  -set property value  set an image property
  -silent              operate silently, i.e. don't ring any bells 
  -snaps value         number of screen snapshots
  -support factor      resize support: > 1.0 is blurry, < 1.0 is sharp
  -synchronize         synchronize image to storage device
  -taint               declare the image as modified
  -transparent-color color
                       transparent color
  -treedepth value     color tree depth
  -verbose             print detailed information about the image
  -virtual-pixel method
                       Constant, Edge, Mirror, or Tile
  -window id           select window with this id or name

Image Operators:
  -annotate geometry text
                       annotate the image with text
  -colors value        preferred number of colors in the image
  -crop geometry       preferred size and location of the cropped image
  -encipher filename   convert plain pixels to cipher pixels
  -geometry geometry   preferred size or location of the image
  -help                print program options
  -monochrome          transform image to black and white
  -negate              replace every pixel with its complementary color 
  -repage geometry     size and location of an image canvas
  -quantize colorspace reduce colors in this colorspace
  -resize geometry     resize the image
  -rotate degrees      apply Paeth rotation to the image
  -strip               strip image of all profiles and comments
  -thumbnail geometry  create a thumbnail of the image
  -transparent color   make this color transparent within the image
  -trim                trim image edges
  -type type           image type

Miscellaneous Options:
  -debug events        display copious debugging information
  -help                print program options
  -list type           print a list of supported option arguments
  -log format          format of debugging information
  -version             print version information

By default, 'file' is written in the MIFF image format.  To
specify a particular image format, precede the filename with an image
format name and a colon (i.e. ps:image) or specify the image type as
the filename suffix (i.e. image.ps).  Specify 'file' as '-' for
standard input or output.
import: delegate library support not built-in `' (X11) @ error/import.c/ImportImageCommand/1303.
./a.py: line 3: syntax error near unexpected token `('
./a.py: line 3: `class List(object):'

What's wrong? Is it an encoding issue?

Answer 1

You are missing the python shebang, #!/usr/bin/env python. Add this as the first line to tell the OS to run your file as a python script and not as a shell script.

Alternatively, run python ./a.py