usage of ":"

[zeppos]

Hi,

I have a question related to the : sign. I have students taking their first steps in Python. I noticed one of my students use ":" wrong. However the code runs fine.

print: float(input("Value?"))

I was wondering if anyone could clarify what "print:" does. Is it i.e. a label? In assembler this is interpreted as a label for a program location in memory.

Thanks

[buran]

It is weird that this actually works. I am surprised myself that this is valid syntax.
In this case print is just a name (i.e. you can replace it with any valid python name), that in this case overrides print function
Then, in my opinion, what you have here is a type annotation or type hint (no matter how weird this may sound, given that it uses 2 function calls, but type hints are ignored by interpreter anyway, as long as they are valid expressions that evaluate without raising exceptions).

You can see that

print: float(input("Value?")) = 'spam'
print('hello')

will produce

Output:
Value?10
Traceback (most recent call last):
  File "c:\Users\BKolev\sandbox\urllibbk.py", line 2, in <module>
    print('hello')
TypeError: 'str' object is not callable

Maybe others would shed more light and/or find a reference to a docs or something