I'm trying to start a for loop after doing something else in python interpreter on the same line, and it throws a SyntaxError when I do so.
>>> a,b = 0, 1;\
... for i in range(1, 10):
File "<stdin>", line 2
for i in range(1, 10):
^
SyntaxError: invalid syntax
Of course I could just execute them separately here, but if I want to have this inside a function definition then I can't exactly do that. What is the correct syntax to do it in the interpreter?
When you have a backslash, you are telling it to ignore the new line. So Python thought your code was a,b = 0, 1 for i in range(1,10):. This is clearly invalid syntax. So, you must remove the semicolon and the backslash. When you want to go to the new line, use shift + enter key.
After that, it should work:
Related
I am new to python and I am having problem over the following syntax:
for x in range(0, 10):
print(x, ' ', end="")
I saw the syntax on a tutorial, however when I try it, it is giving me error. The goal I am trying to reach is printing 0 to 9 while eliminating new line. In other words, print 0 to 9 in a single line. Can you tell me what's wrong with the syntax if there is any?
To print in Python 2.7 without the line break you just need to add an extra comma to the end. It will also add a space between the numbers.
for x in range(0, 10):
print x,
Are you using python 2? Because print() with end keyword argument is a Python 3 command.
The print function with keyword end of Python 3 can be imported into Python 2 by
importing from __future__ at the very beginning of the script:
from __future__ import print_function
However, Python 2's print statement allows a syntax form without parentheses. This syntax will break with this import.
My code always gives invalid syntax errors in different lines. I mean it is giving an error at line 143. Then when I clear that line. It gives the same error at another line. Even I get invalid syntax error at a line like:
print("======================================================================")
How can this be possible? Any ideas?
Thank you ^^
It's hard to know without seeing the whole code. However, be aware that python has implied line continuation with parentheses and other brackets.
This can mean that errors can be reported on a different to that on which the true mistake has been made.
For example:
a = (3 * 4) + (3 * 2
print "Hello"
...gives the error:
File "<ipython-input-1-53e17eda21df>", line 2
print "Hello"
^
SyntaxError: invalid syntax
What is happening is that Python expects the first line to continue, e.g like:
a = (3 * 4) + (3 * 2
+ 100)
...which is completely valid syntax. However, it finds print "Hello" instead, which isn't a valid continuation of the statement inside the brackets.
If I have a file python_error_msg.py
x = [e for e in range(x)
x+=1
And I run it
$ python3 python_error_msg.py
The missing bracket gives the following error:
File "python_error_msg.py", line 2
x+=1
^
SyntaxError: invalid syntax
Why does it happen this way? My error was in forgetting the ] on the list comprehension. Is this something that could be made better, or is it a deeper matter of how Python syntax works?
Also, where can I look in the
codebase
to get an idea of how error reporting works in Python?
The problem is the error isn't official until that second line. Python keeps reading while inside parentheses (or brackets, braces, etc)
What if your code were this?
x = [e for e in range(x)
]
No error.
That said, in these cases I wish SyntaxError would say:
SyntaxError: invalid syntax on line 2 of parenthetical
(After all, even the most experienced programmers forget to close parentheses sometimes
I'm stucked with a Python if-statement. I finished pretty much everything but when running my progarmm, it gives my an syntax error in the first line: I'm so sure I did everything right but as I'm very new to Python and programming at all, it might just be a very foolish mistake...
Thanks for helping guys!
if a == 2:
StartDeckNeighbourright = StartDeck[a + 1]
StartDeckNeighbourright2 = StartDeck[a + 2]
If this isn't the IndentationError that jramirez's answer fixes, but rather an actual SyntaxError, it's probably a problem with the line before the if statement.
In Python, you can continue an expression across multiple lines, as long as the expression is inside parentheses. So, if you accidentally leave off a ) at the end of a function call, or a tuple, or anything else, you often get a mysterious SyntaxError on the next line. For example, this code:
foo = (1, 2
if a == 2:
pass
… will give this error:
if a == 2:
^
SyntaxError: invalid syntax
And just adding another comma moves the error somewhere different!
foo = (1, 2,
if a == 2:
pass
if a == 2:
^
SyntaxError: invalid syntax
Why? Well, even when you understand exactly what these errors mean, they still aren't very helpful. So first, remember:
If you get a SyntaxError on a perfectly valid line, look for a missing ) (or ] or }, or an extra \, or a few other special cases) on the line above.
And if you can get an editor that helps you match up parentheses and brackets, it will make this problem much less likely. (For example, with emacs, at least the way I have it set up, it'll automatically try to indent the if line 7 characters for me, and if I "fix" it it'll fight back against me, and eventually it'll be hard not to notice something is wrong. Then I point at the first ( and it tells me it's unmatched.)
But if you want to know, here goes:
The first version builds a tuple with the value 1, then a value starting with 2 and continuing onto the next line. 2 if a == 2 is a perfectly good beginning for a ternary if expression, but 2 if a == 2: is not; the colon forces it to be an if statement, and you can't put a statement in the middle of an expression.
The second version builds a tuple with the value 1, the value 2, and more values continuing on the next line. if cannot be the start of any valid expression, so you get the SyntaxError earlier. But still not early enough to be useful, of course.
You should post the error you are seeing, however I think all you need is indentation after the if statment
if a == 2:
StartDeckNeighbourright = StartDeck[a + 1]
StartDeckNeighbourright2 = StartDeck[a + 2]
---- four spaces of indentation
In python You must use Indentation:
if a == 2:
StartDeckNeighbourright = StartDeck[a + 1]
StartDeckNeighbourright2 = StartDeck[a + 2]
I am getting invalid syntax error in my python script for this statement
44 f = open(filename, 'r')
45 return
return
^
SyntaxError: invalid syntax
I am not sure what exactly is wrong here? I am a python newbie and so will greatly appreciate if someone can please help.
I am using version 2.3.4
I had the same problem. Here was my code:
def gccontent(genomefile):
nbases = 0
totalbases = 0
GC = 0
for line in genomefile.xreadlines():
nbases += count(seq, 'N')
totalbases += len(line)
GC += count(line, 'G' or 'C')
gcpercent = (float(GC)/(totalbases - nbases)*100
return gcpercent
'return'was invalid syntax
I simply failed to close the bracket on the following code:
gcpercent = (float(GC)/(totalbases - nbases)*100
Hope this helps.
I got an "Invalid Syntax" on return when I forgot to close the bracket on my code.
elif year1==year2 and month1 != month2:
total_days = (30-day1)+(day2)+((month2-(month1+1))*30
return (total_days)
Invalid syntax on return.
((month2-(month1+1))*30 <---- there should be another bracket
((month2-(month1+1)))*30
Now my code works.
They should improve python to tell you if you forgot to close your brackets instead of having an "invalid" syntax on return.
Getting "invalid syntax" on a plain return statement is pretty much impossible. If you use it outside of a function, you get 'return' outside function, if you have the wrong indentation you get IndentationError, etc.
The only way I can get a SyntaxError: invalid syntax on a return statement, is if in fact it doesn't say return at all, but if it contains non-ascii characters, such as retürn. That give this error. Now, how can you have that error without seeing it? Again, the only idea I can come up with is that you in fact have indentation, but that this indentation is not spaces or tabs. You can for example have somehow inserted a non-breaking space in your code.
Yes, this can happen. Yes, I have had that happen to me. Yes, you get SyntaxError: invalid syntax.
i just looked this up because i was having the same problem (invalid syntax error on plan return statement), and i am extremely new at python (first month) so i have no idea what i'm doing most of the time.
well i found my error, i had forgotten an ending parentheses on the previous line. try checking the end of the previous line for a forgotten parentheses or quote?
>>> 45 return
File "<stdin>", line 1
45 return
^
SyntaxError: invalid syntax
>>>
That might explain it. It doesn't explain the 44 f = open(filename, 'r'), but I suspect that someone copied and pasted 45 lines of code where the indentation was lost and line numbers included.
Usually it's a parenthetical syntax error. Check around the error.
I encountered a similar problem by trying to return a simple variable assignation within an "if" block.
elif len(available_spots)==0:
return score=0
That would give me a syntax error. I fixed it simply by adding a statement before the return
elif len(available_spots)==0:
score=0
return score
I had the same problem. The issue in my case was, that i mixed up datatypes in my return statement. E.g.
return string + list + string