Python Forum

this little test script works:

Output:
lt2a/phil /home/phil 137> cat try.py
#!/usr/bin/env python3
a=[1,2,3,4,5,6]
b=[0,5,10]
for x in b:
    if x in a:
        print('foo')
        break
else:
    print('bar')
print('xyzzy')
lt2a/phil /home/phil 138> python3 try.py
foo
xyzzy
lt2a/phil /home/phil 139>

however, doing the same exact thing interactively gets a syntax error:

Output:
lt2a/phil /home/phil 139> python3
Python 3.6.8 (default, Jan 14 2019, 11:02:34) 
[GCC 8.0.1 20180414 (experimental) [trunk revision 259383]] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> a=[1,2,3,4,5,6]
>>> b=[0,5,10]
>>> for x in b:
...     if x in a:
...         print('foo')
...         break
... else:
...     print('bar')
... print('xyzzy')
  File "<stdin>", line 7
    print('xyzzy')
        ^
SyntaxError: invalid syntax
>>>

any idea what is wrong?

The interactive interpreter wants you to end the for loop with a blank line before continuing on with more code:

Output:
>>> for i in range(5):
...     print(i)
... print(0)
  File "<stdin>", line 3
    print(0)
        ^
SyntaxError: invalid syntax
>>> for i in range(5):
...     print(i)
...
0
1
2
3
4
>>> print(0)
0

that doesn't work, either:

Output:
Python 3.6.8 (default, Jan 14 2019, 11:02:34) 
[GCC 8.0.1 20180414 (experimental) [trunk revision 259383]] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> a=[1,2,3,4,9,6]
>>> b=[0,5,10]
>>> for x in b:
...     if x in a:
...         print('foo')
...         break
... 
>>> else:
  File "<stdin>", line 1
    else:
       ^
SyntaxError: invalid syntax
>>>

The end of a for/else is after the else block:

>>> a=[1,2,3,4,5,6]
>>> b=[0,5,10]
>>> for x in b:
...     if x in a:
...         print('foo')
...         break
... else:
...     print('bar')
...
foo
>>> print('xyzzy')
xyzzy

why does the interactive interpreter use a different syntax than the script interpreter?