Using bash echo command to input into a python one liner

Question

I am trying to input a string using echo into a Python one liner then perform a Caeasar's Cipher on the string.

One of the examples my instructor gave me was this.

~ $ echo "Hello Holly." | python -c "import sys; [print(line) for line in sys.stdin]"

The output is suppose to be: Hello Holly.

How ever when I type the command in I get:

File "<string>", line 1
 import sys; [print(line) for line in sys.stdin]
                  ^
SyntaxError: invalid syntax

I would appreciate it if someone could point out the error to me. I am using Python 2.6 on Centos 6.

Thanks.

Using list comprehensions simply to apply a function to each item in a list without caring about the resulting list is a bad habit to get into; shame on your instructor. Use ... | python -c 'import sys; print "".join(sys.stdin)' instead. — chepner
– chepner, Commented Mar 3, 2014 at 18:15

MattDMo · Accepted Answer · 2014-03-03 16:57:30Z

6

In Python 2 print is a statement, not a function. Try this instead:

echo "Hello Holly." | python -c "import sys; print [line for line in sys.stdin]"

Alternatively, you could use the following to just print plain text (thanks @mgilson):

echo "Hello Holly." | python -c "import sys; print ' '.join([line for line in sys.stdin])"

edited Mar 3, 2014 at 16:57

answered Mar 3, 2014 at 16:50

MattDMo

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8 Comments

Justin C Over a year ago

Just to elaborate, using Python 3, OP's implementation will work :)

mgilson Over a year ago

Looks OK now, but you're printing a list, not plain text as OP wants. The cleanest is to probably ' '.join it or something...

mgilson Over a year ago

@JustinC -- That's not always the case... it depends on how you compile, etc.

Bob Glidewell Over a year ago

bob@pbx:~ $ echo "Hello Holly." | python -c " import sys; print [line for line in sys.stdin]" File "<string>", line 1 import sys; print [line for line in sys.stdin] ^ IndentationError: unexpected indent

MattDMo Over a year ago

@user3375720 make sure you copy and paste directly. It works fine for me using Python 2.6 on CentOS 6. It looks like you have a space between the " following python -c and import - that's probably what's causing the IndentationError.

|

Cam · Accepted Answer · 2014-03-03 16:53:53Z

0

It looks like you are using python2 while your isntructor is using python 3.

answered Mar 3, 2014 at 16:53

Cam

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