Splitting Strings within an Array

Question

I am writing a program in python that reads in a text file and executes any python commands within it. The commands may be out of order, but each command has a letter ID such as {% (c) print x %}

I've been able to sort all the commands with in the document into an array, in the correct order. My question is, how to i remove the (c), so i can run exec(statement) on the string?

Here is the full example array

[' (a) import random ', ' (b) x = random.randint(1,6) ', ' (c) print x ', ' (d) print 2*x ']

Also, I am very new to python, my first assignment with it.

Split, take all but the first, second, and last, then join with spaces — Brian, Mar 15 '17 at 03:35
Possible duplicate of [How to delete a character from a string using python?](http://stackoverflow.com/questions/3559559/how-to-delete-a-character-from-a-string-using-python) — TessellatingHeckler, Mar 15 '17 at 03:38
`exec(statement[5:])` try this it will help .. i tried to get substring so that it doesnot include the (a) — Ankur Jyoti Phukan, Mar 15 '17 at 03:40

score 1 · Answer 1 · answered Mar 15 '17 at 03:44

1

Take everything right to the parenthesis and exec:

for cmd in arr:
    exec(cmd.split(") ")[-1])

answered Mar 15 '17 at 03:44

Marat

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I see how this works, and I like it. How ever I get an invalid syntax error for my for loop. I used my own variables of course, but once I figure that error out I will probably use this. – sbowde4 Mar 15 '17 at 03:48

score 1 · Accepted Answer · answered Mar 15 '17 at 03:46

1

You can remove the index part, by using substring:

for cmd in arr:
   exec(cmd[5:])

answered Mar 15 '17 at 03:46

Ankur Jyoti Phukan

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1

This was the quickest method, and it worked the best because I didn't want to completely remove the index. On account of it will be used later. – sbowde4 Mar 15 '17 at 03:59
It is nice that it is short, quick and easily explained :-) However, a regex approach will survive changes to the whitespace and having a command-id of more than one character for a bigger input. – Raymond Hettinger Mar 15 '17 at 04:10

Raymond Hettinger · Answer 3 · 2017-03-15T03:56:11.913

Stripping the command-id prefixes is a good job for a regular expression:

>>> import re
>>> commands = [' (a) import random ', ' (b) x = random.randint(1,6) ', ' (c) print x ', ' (d) print 2*x ']
>>> [re.search(r'.*?\)\s*(.*)', command).group(1) for command in commands]
['import random ', 'x = random.randint(1,6) ', 'print x ', 'print 2*x ']

The meaning of regex components are:

.*?\) means "Get the shortest group of any characters that ends with a closing-parentheses."
\s* means "Zero or more space characters."
(.*) means "Collect all the remaining characters into group(1)."

How this explanation makes it all clear :-)

score 0 · Answer 4 · answered Mar 15 '17 at 03:45

Since the pattern looks simple and consistent, you could use regex.

This also allows for both (a) and (abc123) as valid IDs.

import re

lines = [
    ' (a) import random ',
    ' (b) x = random.randint(1,6) ',
    ' (c) print x ',
    ' (d) print 2*x '
]

for line in lines:
    print(re.sub(r"^[ \t]+(\(\w+\))", "", line))

Which would output:

 import random 
 x = random.randint(1,6) 
 print x 
 print 2*x

If you really only want to match a single letter, then replace \w+ with [a-zA-Z].

score 0 · Answer 5 · answered Mar 15 '17 at 03:45

0

You may use a simple regex to omit the first alpha character in braces as:

import re

lst = [' (a) import random ', ' (b) x = random.randint(1,6) ', ' (c) print x ', ' (d) print 2*x ']

for ele in lst:
    print re.sub("^ \([a-z]\)", "", ele)

answered Mar 15 '17 at 03:45

ZdaR

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Splitting Strings within an Array

5 Answers5