Converting a RGB color tuple to a six digit code

Question

Use the format operator %:

>>> '#%02x%02x%02x' % (0, 128, 64)
'#008040'

Note that it won't check bounds...

>>> '#%02x%02x%02x' % (0, -1, 9999)
'#00-1270f'

def clamp(x): 
  return max(0, min(x, 255))

"#{0:02x}{1:02x}{2:02x}".format(clamp(r), clamp(g), clamp(b))

This uses the preferred method of string formatting, as described in PEP 3101. It also uses min() and max to ensure that 0 <= {r,g,b} <= 255.

Update added the clamp function as suggested below.

Update From the title of the question and the context given, it should be obvious that this expects 3 ints in [0,255] and will always return a color when passed 3 such ints. However, from the comments, this may not be obvious to everyone, so let it be explicitly stated:

Provided three int values, this will return a valid hex triplet representing a color. If those values are between [0,255], then it will treat those as RGB values and return the color corresponding to those values.

This is an old question but for information, I developed a package with some utilities related to colors and colormaps and contains the rgb2hex function you were looking to convert triplet into hexa value (which can be found in many other packages, e.g. matplotlib). It's on pypi

pip install colormap

and then

>>> from colormap import rgb2hex
>>> rgb2hex(0, 128, 64)
'##008040'

Validity of the inputs is checked (values must be between 0 and 255).

I have created a full python program for it the following functions can convert rgb to hex and vice versa.

def rgb2hex(r,g,b):
    return "#{:02x}{:02x}{:02x}".format(r,g,b)

def hex2rgb(hexcode):
    return tuple(map(ord,hexcode[1:].decode('hex')))

You can see the full code and tutorial at the following link : RGB to Hex and Hex to RGB conversion using Python

triplet = (0, 128, 64)
print '#'+''.join(map(chr, triplet)).encode('hex')

or

from struct import pack
print '#'+pack("BBB",*triplet).encode('hex')

python3 is slightly different

from base64 import b16encode
print(b'#'+b16encode(bytes(triplet)))

I'm truly surprised no one suggested this approach:

For Python 2 and 3:

'#' + ''.join('{:02X}'.format(i) for i in colortuple)

Python 3.6+:

'#' + ''.join(f'{i:02X}' for i in colortuple)

As a function:

def hextriplet(colortuple):
    return '#' + ''.join(f'{i:02X}' for i in colortuple)

color = (0, 128, 64)
print(hextriplet(color))

#008040

Here is a more complete function for handling situations in which you may have RGB values in the range [0,1] or the range [0,255].

def RGBtoHex(vals, rgbtype=1):
  """Converts RGB values in a variety of formats to Hex values.

     @param  vals     An RGB/RGBA tuple
     @param  rgbtype  Valid valus are:
                          1 - Inputs are in the range 0 to 1
                        256 - Inputs are in the range 0 to 255

     @return A hex string in the form '#RRGGBB' or '#RRGGBBAA'
"""

  if len(vals)!=3 and len(vals)!=4:
    raise Exception("RGB or RGBA inputs to RGBtoHex must have three or four elements!")
  if rgbtype!=1 and rgbtype!=256:
    raise Exception("rgbtype must be 1 or 256!")

  #Convert from 0-1 RGB/RGBA to 0-255 RGB/RGBA
  if rgbtype==1:
    vals = [255*x for x in vals]

  #Ensure values are rounded integers, convert to hex, and concatenate
  return '#' + ''.join(['{:02X}'.format(int(round(x))) for x in vals])

print(RGBtoHex((0.1,0.3,  1)))
print(RGBtoHex((0.8,0.5,  0)))
print(RGBtoHex((  3, 20,147), rgbtype=256))
print(RGBtoHex((  3, 20,147,43), rgbtype=256))