Weird behaviour with semicolon before function call in IPython and Jupyter Notebook
Question:
I stumbled upon some strange behaviour using Jupyter Notebook and wondered what, if any, the purpose was. If you enter a semicolon before a function call, you get the result of applying the function to a string which reflects all the code after the function name. For example, if I do ;list('ab') I get the result of list("('ab')") :
In [138]: ;list('ab')
Out[138]:
['(', "'", 'a', 'b', "'", ')']
I’m using Jupyter with IPython 4. It happens in IPython as well as Jupyter Notebook.
Is it intended and, if so, why?
Answers:
It’s a command for automatic quoting of function arguments: Automatic parentheses and quotes
From the documentation:
You can force automatic quoting of a function’s arguments by using ,
or ; as the first character of a line. For example:
In [1]: ,my_function /home/me # becomes my_function("/home/me")
If you use ‘;’ the whole argument is quoted as a single string, while
‘,’ splits on whitespace:
In [2]: ,my_function a b c # becomes my_function("a","b","c")
In [3]: ;my_function a b c # becomes my_function("a b c")
Note that the ‘,’ or ‘;’ MUST be the first character on the line! This
won’t work:
In [4]: x = ,my_function /home/me # syntax error
In your case, it’s quoting all characters, including ' and ( and ).
You get similar output here, but without the single quotes:
In [279]:
;list(ab)
Out[279]:
['(', 'a', 'b', ')']
I stumbled upon some strange behaviour using Jupyter Notebook and wondered what, if any, the purpose was. If you enter a semicolon before a function call, you get the result of applying the function to a string which reflects all the code after the function name. For example, if I do ;list('ab') I get the result of list("('ab')") :
In [138]: ;list('ab')
Out[138]:
['(', "'", 'a', 'b', "'", ')']
I’m using Jupyter with IPython 4. It happens in IPython as well as Jupyter Notebook.
Is it intended and, if so, why?
It’s a command for automatic quoting of function arguments: Automatic parentheses and quotes
From the documentation:
You can force automatic quoting of a function’s arguments by using ,
or ; as the first character of a line. For example:
In [1]: ,my_function /home/me # becomes my_function("/home/me")
If you use ‘;’ the whole argument is quoted as a single string, while
‘,’ splits on whitespace:
In [2]: ,my_function a b c # becomes my_function("a","b","c")
In [3]: ;my_function a b c # becomes my_function("a b c")
Note that the ‘,’ or ‘;’ MUST be the first character on the line! This
won’t work:
In [4]: x = ,my_function /home/me # syntax error
In your case, it’s quoting all characters, including ' and ( and ).
You get similar output here, but without the single quotes:
In [279]:
;list(ab)
Out[279]:
['(', 'a', 'b', ')']