py

Python as a pipeline tool for command-line ninjas.

cat notes.txt | py 'line.replace("awk", "py")'

Installation

Just place the bin/py file somewhere in your PATH, and make it executable.

You will need a python executable in the environment (/usr/bin/env python). Python 2 and 3 are both supported.

Basic usage

With no input or flags, py executes inline python expresions:

$ py '1 + 2'
3

Modules are imported automatically, including from the current directory.

$ py 'math.factorial(6)'
720

Processing input

py has three input handling modes, selected automatically when special variable names are used in the expression.

The type of each variable is dependent on the Python version:

• TextType is unicode in Python 2, str in Python 3
• BinaryType is str in Python 2, bytes in Python 3

Variable	Input mode
line	Eval expression for each line of input, assigning each to line in TextType
lines	Eval expression once, assigning a list of input lines to lines
input	Eval expression once, assigning the entire input to input
bline	As line, but in BinaryType
blines	As lines, but with each item in BinaryType
binput	As input, but in BinaryType

So you can do:

# Replace a word in all lines:
$ ... | py 'line.replace("foo", "bar")'  

# Print longest line:
$ ... | py 'max(lines, key=lambda l: len(l))' 

# Hex-encode entire input:
$ ... | py 'binascii.hexlify(binput)'

You can only use one of the three magic variable pairs inside your expression. For example, it's OK to use both line and bline, but not line and input.