Pfthb

So, I want to write this program where I define a class, and the method within it takes a list of colours as an argument. The colours "red", "Red, "green" and "Green" should be replaced with "black", "Black", "white" and "White" (see the dictionary "self.colour_replacement" in the code-text).

If only one of the two colors red/green regardsless of capital letter, is in the list, the program should only return the list without changing it.

Example_1:
print(c.make_readable(['Green', 'Green', 'pink', 'green', 'yellow', 'green', 
'green']))

should return: 
['Green', 'Green', 'pink', 'green', 'yellow', 'green', 'green']


Example_2: 
print(c.make_readable(['green', 'Green']))

should return:
['green', 'Green']

I think the problem has to do with my "or" and "and" statements in the line:

if ('red' and 'green') in colours or ('Red' and 'green') in colours or 
('red' and 'Green') in colours or ('Red' and 'Green') in colours: 

but I am not entirely sure.

class ColourChanger:
 def __init__(self):
 """A dictionary that shows the 
 replacement colours."""
 self.colour_replacement = 'Green' : 'White', 'red': 'black', 
 'green': 'white', 'Red' : 'Black'

 def make_readable(self, colours):
 result = 
 if ('red' and 'green') in colours or ('Red' and 'green') in colours or 
 ('red' and 'Green') in colours or ('Red' and 'Green') in colours:
 for col in colours:
 if col in self.colour_replacement:
 result.append(self.colour_replacement[col]) """Appends the 
 "result"-list with the replacement color instead of the color (col)."""
 else:
 result.append(col)

 else:
 return colours

 return result


c = ColourChanger()
print(c.make_readable(['green', 'Green']))
print(c.make_readable(['Red', 'red']))
print(c.make_readable(['Red', 'Red', 'pink', 'red', 'yellow', 'red', 'red', 
'Green']))
print(c.make_readable(['Green', 'Green', 'pink', 'green', 'yellow', 'green', 
'green']))


Expected output:
['green', 'Green']
['Red', 'red']
['Black', 'Black', 'pink', 'black', 'yellow', 'black', 'black', 'White']
['Green', 'Green', 'pink', 'green', 'yellow', 'green', 'green']

Actual Output: 
['white', 'White']
['Red', 'red']
['Black', 'Black', 'pink', 'black', 'yellow', 'black', 'black', 'White']
['White', 'White', 'pink', 'white', 'yellow', 'white', 'white']

Your condition is wrong, to fix it use

if ('red' in colours and 'green' in colours) or ( ...) .... : 

but its not needed - as much is shared in the dupe.

You can avoid most of your ifs alltogether. There is very few benefit in checking first if something is in the list and then conditionally build the replacement to return it. You might sometimes omit building the replacement list which can be a benefit if your lists are huge but you will still have to iterate each list once to its full length to "see" this. You will also need to do this for all lists that would need to get a substitute list to be built - thouse would be traversed more then once - eating up all the "time" you saved for those that do not need replacements. For short(ish) lists its easier to simply build the replacement every time:

It is easier to build the "replace" on the first run through your data:

class ColourChanger:
 def __init__(self):
 # A dictionary that shows the replacement colours - only lowercase needed
 self.colour_replacement = 'green' : 'white', 'red': 'black'

 def make_readable(self, colours):
 result = 

 # iterate all col's, append them if not in dict, else append the replacement
 for col in colours:
 replace = self.colour_replacement.get(col.lower(), col)

 # adjust case-ness by string-splicing with uppercase where needed
 if col[0].isupper() and replace[0].islower(): 
 replace = replace[0].upper()+replace[1:]

 result.append(replace)

 return result



c = ColourChanger()
print(c.make_readable(['green', 'Green']))
print(c.make_readable(['Red', 'red']))
print(c.make_readable(['Red', 'Red', 'pink', 'red', 'yellow', 'red', 'red', 
'Green']))
print(c.make_readable(['Green', 'Green', 'pink', 'green', 'yellow', 'green', 
'green']))

Output:

['white', 'White']
['Black', 'black']
['Black', 'Black', 'pink', 'black', 'yellow', 'black', 'black', 'White']
['White', 'White', 'pink', 'white', 'yellow', 'white', 'white']

See Why dict.get(key) instead of dict[key]? for why using .get(key, default).