Missleading Python Error Message - python

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

Related

Using os.("start ...) with variable file name. python

The code:
doc.save("AttendanceReportFor"+EventNameSTR+".docx")
os.("start AttendanceReportFor"+EventNameSTR+".docx")
Where:
EventNameSTR=("Juilie")
Results in
SyntaxError: invalid syntax
In the line
os.("start AttendanceReportFor"+EventNameSTR+".docx")
Is it possible for the os() to take variables in its command statement?
The expected result is opening the word document in Microsoft Word.
your problem is that you are using : os.("start AttendanceReportFor"+EventNameSTR+".docx") which is, as the error says: a syntax error, since you can't use os.(....) - you should use :
os.system(command) or subprocess.Popen(args....)

python invalid syntax everytime

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.

Python dictionary SyntaxError

I'm moving to Python from PHP and I seem to be stuck in my first hour of learning Python.
This seems to be such a basic question that I'm having trouble finding an answer - so please forgive me.
When I try to create a dictionary I enter:
numbers = ('Bob':'322', 'Mary':'110', 'Joe':'839')
I get the error:
File "<stdin>", line 1
numbers = ('Bob':'322', 'Mary':'110', 'Joe':'839')
^
SyntaxError: invalid syntax
I've tried this in both the command line and in IDLE and the same error appears. What am I doing wrong? I really can't see it. Again sorry for low level of this question.
Dictionaries use curly braces {}, not parentheses ()
numbers = {'Bob':'322', 'Mary':'110', 'Joe':'839'}

appending two variables in os.path.isdir

I am trying to append two variables BUILD_ROOT_DIR and W_ROOT and check if this directory exists ,if not raise a flag...running into following syntax error while appending..what is wrong here?
if(os.path.isdir(BUILD_ROOT_DIR + W_ROOT))
raise
if(os.path.isdir(BUILD_ROOT_DIR + W_ROOT))
^
SyntaxError: invalid syntax
You need a colon to end the if statement (the parentheses are not required):
if os.path.isdir(BUILD_ROOT_DIR + W_ROOT):
raise
God gave you ':' for ending an if clause and he also told you: keep this Python tutorial under your pillow and read it all night before sleeping.
http://docs.python.org/2/tutorial/controlflow.html#if-statements

Strange error about invalid syntax

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

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