Question:
I’m having problems reading text files into my python programs.
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import sys words = sys.stdin.readlines() |
I’m reading the file in through stdin but when I try to execute the program I’m getting this error.
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PS> python evil_61.py < evilwords.txt At line:1 char:19 + python evil_61.py < evilwords.txt + ~ The '<' operator is reserved for future use. + CategoryInfo : ParserError: (:) [], ParentContainsErrorRecordException + FullyQualifiedErrorId : RedirectionNotSupported |
Could someone tell me how to run these kinds of programs as it is essential for my course and I’d rather use Windows than Linux.
Answer:
Since < for input redirection is not supported in PowerShell, use Get-Content in a pipeline instead:
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Get-Content evilwords.txt | python evil_61.py |
Note: Adding the -Raw switch – which reads a file as a single, multi-line string – would speed things up in principle (at the expense of increased memory consumption), but PowerShell invariably appends a newline to data piped to external programs, as of PowerShell 7.2 (see this answer), so the target program will typically see an extra, empty line at the end. Get-Content‘s default behavior of line-by-line streaming avoids that.
Beware character-encoding issues:
Get-Content, in the absence of an-Encodingargument, assumes the following encoding:- Windows PowerShell (the built-into-Windows edition whose latest and final version is 5.1): the active ANSI code page, which is implied by the active legacy system locale (language for non-Unicode programs).
- PowerShell (Core) 7+: (BOM-less) UTF-8
- On passing the lines through the pipeline, they are (re-)encoded based on the encoding stored in the
$OutputEncodingpreference variable, which defaults to:- Windows PowerShell: ASCII(!)
- PowerShell (Core) 7+: (BOM-less) UTF-8
As you can see, only PowerShell (Core) 7+ exhibits consistent behavior, though, unfortunately, as of PowerShell Core 7.2.0-preview.9, this doesn’t yet extend to capturing output from external programs, because the encoding that controls the interpretation of received data, stored in [Console]::OutputEncoding], still defaults to the system’s active OEM code page – see GitHub issue #7233.