f-strings and backslashes

[newbieAuggie2019]

Hi!

If I run this:

string5 = '''Dear Alice,
How have you been? I am fine.
There is a container in the fridge
that is labeled "Milk Experiment".
Please do not drink it.
Sincerely,
Bob'''
string6 = '\n'

print(f"Applying string5.split('a') to 'string5' results in: {string5.split('a')}")

it works and produces this output:

Output:
Applying string5.split('a') to 'string5' results in: ['De', 'r Alice,\nHow h', 've you been? I ', 'm fine.\nThere is ', ' cont', 'iner in the fridge\nth', 't is l', 'beled "Milk Experiment".\nPle', 'se do not drink it.\nSincerely,\nBob']

But it seems that f-strings and backslashes don't like each other, so:

string5 = '''Dear Alice,
How have you been? I am fine.
There is a container in the fridge
that is labeled "Milk Experiment".
Please do not drink it.
Sincerely,
Bob'''
string6 = '\n'

print(f"Applying string5.split('\n') to 'string5' results in: {string5.split('\n')}")

produces the following:

Error:
SyntaxError: f-string expression part cannot include a backslash.

I read somewhere that creating a string with the value of '\n' was a trick to avoid that error. So I tried:

string5 = '''Dear Alice,
How have you been? I am fine.
There is a container in the fridge
that is labeled "Milk Experiment".
Please do not drink it.
Sincerely,
Bob'''
string6 = '\n'

print(f"Applying string5.split({string6}) to 'string5' results in: {string5.split({string6})}")

but it doesn't do the trick and it shows the following error message:

Error:
Traceback (most recent call last):
  File "C:/Users/User1/AppData/Local/Programs/Python/Python37/atbs_06_checkingStrings_04.py", line 10, in <module>
    print(f"Applying string5.split({string6}) to 'string5' results in: {string5.split({string6})}")
TypeError: must be str or None, not set

So now I have 2 doubts:
1) How to separate the multiline string by the new line escape ('\n')?
2) Why the error does say 'must be str or None, not set'? (Supposedly string6 is a string (string6 = '\n') and not a set).

Thank you and all the best,

[buran]

i guess you want

print(f"Applying string5.split({repr(string6)}) to 'string5' results in: {string5.split(string6)}")

[newbieAuggie2019]

i guess you want

print(f"Applying string5.split({repr(string6)}) to 'string5' results in: {string5.split(string6)}")

Thank you!

It works, although I don't fully understand the repr() function. It seems to be related somehow to str() and even ... to magic!!!

I tried to see the difference with this:

string7 = 'Paris is the capital of France.'

print(f"This is with str(): {str(string7)}")
print(f"This is with str(): {str(5.0/2.0)}")
print(f"This is with repr(): {repr(string7)}")
print(f"This is with repr(): {repr(5.0/2.0)}")

producing this output:

Output:
This is with str(): Paris is the capital of France.
This is with str(): 2.5
This is with repr(): 'Paris is the capital of France.'
This is with repr(): 2.5

where it seems to me that the only difference is that the repr() function puts the string between quotes.

I checked also the built-in help, which I don't usually do, as it seems like Chinese to me:

Output:
>>> help(repr)
Help on built-in function repr in module builtins:

repr(obj, /)
    Return the canonical string representation of the object.
    
    For many object types, including most builtins, eval(repr(obj)) == obj.

so I guess that's also why I don't fully understand it ... it returns the canonical string representation of the object ... and I'm just a layman ...

I see that you simplified also some part of my code, eliminating problems that I usually have. My code:

print(f"Applying string5.split({string6}) to 'string5' results in: {string5.split({string6})}")

Your code:

print(f"Applying string5.split({repr(string6)}) to 'string5' results in: {string5.split(string6)}")

where {string5.split({string6})} has been simplified to {string5.split(string6)}. I tend to substitute things between curly braces "{}", but it seems that when it is a substitution inside another substitution, my curly braces produce an error or something not working properly. It looks like that when it is a substitution inside another substitution, I have to eliminate the curly braces from the inner substitution. Is that right?

Thanks and all the best,

[buran]

you need to use repr() because otherwise the new line \n will be "translated" in actual new line in the output (i.e. the output will be split on 2 lines)

[DeaD_EyE]

Why not using the method splitlines?

print(f"Applying string5.splitlines to 'string5' results in: {string5.splitlines()}")

[buran]

Why not using the method splitlines?

my understanding was they OP wants flexibility - split at arbitrary char, not just line ends. Otherwise first part of the output doesn't make sense to use f-string to output what split char is, it could be hardcoded