I am trying to load a .txt file containing a very large number into SageMath for factoring. I am new to this and have tried every single method I can find on the web getting a different error every time. Can someone please talk me through this?
Toy solution :
Create an example :
sage: # Let's generate (the string representation of) a large integer
sage: foo=str(frac(pi).n(digits=3000))
sage: # Put that (except the initial "0.") on a file
sage: f=open("pifrac.txt", "w", encoding="utf8")
sage: f.write("%s\n"%foo[2:])
3001
sage: f.close()Read that string :
sage: # Read that back in a string
sage: f=open("pifrac.txt", "r", encoding="utf8")
sage: bar=f.readline()
sage: f.close()Convert it :
sage: gee=eval("Integer(%s)"%bar)Check it :
sage: # What's that ?
sage: type(gee)
<class 'sage.rings.integer.Integer'>
sage: # Magnitude ?
sage: gee.log(10).n()
2999.15104072095Check again :
sage: (frac(pi).n(digits=3000)-gee*1e-3000).log(10)
-infinityRight...
HTH,
The error
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 2-3: truncated \UXXXXXXXX escape
can be seen even at Sagecell, where the file itself is missing. However, the error is not about the file content but about its name, which contains escape characters (backslashes). Either each of them must be doubled, or the whole string must be declared as raw:
f=open(r"C:\Users\karen\Desktop\factcipher.txt", "r", encoding="utf8")Note the r in front of the opening quotation mark.
With
Sage: foo=str(frac(pi).n(digits=13048009))
Sage: f=open(r"C:\Users\karen\Desktop\factcipher.txt", "r", encoding="utf8")
I get error FileNotFoundError: [Errno 2] No such file or directory: 'C:\Users\karen\Desktop\factcipher.txt'
I’m sure the filename and path is correct as I opened the properties and copied the location from there.
Then you have a discrepancy somewhere in the file path/name. E.g. it may contain a space at the end of its name or a character that is different from one of those listed (eg., e instead of é) or alike.
Hi Max I appreciate your help. I've checked the file path about 100 times for spaces etc and I've copied and pasted it from the properties. I can't see how it can have an error. I've heard of people having problems with permissions for sage to access folders. Could it be that? the error I posted above I copied and pasted from Sage, and there are definitely no spaces or special characters, at least that are visible. I'm getting really frustrated.
Can you check what import os; print(os.sep) says?
sage: import os; print(os.sep)
/
sage:
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Last updated: Mar 01
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Can you provide a toy example? Does your .txt file just contain something like "1023", or is there more in it than just a number?
It is a number over 13,000,000 digits long. It is the product of powers of up to the first 26 primes and I need to factor it.
When I put in the second line below: f=open("C:\Users\karen\Desktop\factcipher.txt", "w", encoding="utf8") I get SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 2-3: truncated \UXXXXXXXX escape
The above command should be sage: f=open("C:\Users\karen\Desktop\factcipher.txt", "w", encoding="utf8")
Are you sure it's a text file? The error suggest there are some non-text characters.