Handle Windows paths in Python
David Y.
—The Problem
I’m getting a strange error when attempting to open a file with Python on Windows. Here’s my code:
import csv data = open("C:\Users\sam\Documents\data\1.5\data.csv") data = csv.reader(data) print(data)
When I try to execute it, I get this error:
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 2-3: truncated \UXXXXXXXX escape
The Solution
The error is caused by the backslash character (\) that is used by Python for escape sequences to represent special characters, for example, \n for new line. The error message indicates that Python is attempting to interpret the \User section of the path string as a Unicode code point because it starts with \U.
We can get around this in a few different ways.
Use Raw Strings
By placing an r in front of a string, we instruct Python not to look for escape sequences within it, and thus force it to treat any backslashes as literal backslashes.
import csv data = open(r"C:\Users\sam\Documents\data\1.5\data.csv") data = csv.reader(data) print(data)
Use Forward Slashes
File paths on Mac and *nix-based systems use forward slashes rather than backslashes to denote folder structure. Python allows us to do this on Windows as well:
import csv data = open("C:/Users/sam/Documents/data/1.5/data.csv") data = csv.reader(data) print(data)
This approach has the advantage of making partial or relative path strings work across platforms. For example, the path sam/Documents/data/1.5/data.csv could be resolved to /home/sam/Documents/data/1.5/data.csv on a Linux system or C:\Users\sam\Documents\data\1.5\data.csv on a Windows system, as long as the script is executed in /home/ or C:\Users.
Use Double Backslashes
In a standard Python string, the escape sequence \\ translates to \. Therefore, a third way we can resolve this problem is by replacing all \s with \\s in the path.
import csv data = open("C:\\Users\\sam\\Documents\\data\\1.5\\data.csv") data = csv.reader(data) print(data)
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