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Traverse a list in reverse order in Python
...
Use the built-in reversed() function:
>>> a = ["foo", "bar", "baz"]
>>> for i in reversed(a):
... print(i)
...
baz
bar
foo
To also access the original index, use enumerate() on your list before passing it to reversed():
>>> for i, e in reversed(li...
How do I set a variable to the output of a command in Bash?
...rs which could be interpreted as part of the variable name. e.g. ${OUTPUT}foo. They are also required when performing inline string operations on the variable, such as ${OUTPUT/foo/bar}
– rich remer
Jun 1 '16 at 23:16
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Count number of occurrences of a pattern in a file (even on same line)
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To count all occurrences, use -o. Try this:
echo afoobarfoobar | grep -o foo | wc -l
And man grep of course (:
Update
Some suggest to use just grep -co foo instead of grep -o foo | wc -l.
Don't.
This shortcut won't work in all cases. Man page says:
-c print a count of...
Converting a Java Keystore into PEM Format
... pretty straightforward, using jdk6 at least...
bash$ keytool -keystore foo.jks -genkeypair -alias foo \
-dname 'CN=foo.example.com,L=Melbourne,ST=Victoria,C=AU'
Enter keystore password:
Re-enter new password:
Enter key password for
(RETURN if same as keystore password):
bas...
How can I recursively find all files in current and subfolders based on wildcard matching?
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Use find for that:
find . -name "foo*"
find needs a starting point, and the . (dot) points to the current directory.
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Finding the index of an item in a list
Given a list ["foo", "bar", "baz"] and an item in the list "bar" , how do I get its index ( 1 ) in Python?
31 Answers
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Why does += behave unexpectedly on lists?
...unction will append all elements of the parameter to the list.
When doing foo += something you're modifying the list foo in place, thus you don't change the reference that the name foo points to, but you're changing the list object directly. With foo = foo + something, you're actually creating a ne...
count (non-blank) lines-of-code in bash
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cat foo.c | sed '/^\s*$/d' | wc -l
And if you consider comments blank lines:
cat foo.pl | sed '/^\s*#/d;/^\s*$/d' | wc -l
Although, that's language dependent.
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How would you make a comma-separated string from a list of strings?
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Why the map/lambda magic? Doesn't this work?
>>> foo = ['a', 'b', 'c']
>>> print(','.join(foo))
a,b,c
>>> print(','.join([]))
>>> print(','.join(['a']))
a
In case if there are numbers in the list, you could use list comprehension:
>>>...
Does Java support default parameter values?
...l ways to simulate default parameters in Java:
Method overloading.
void foo(String a, Integer b) {
//...
}
void foo(String a) {
foo(a, 0); // here, 0 is a default value for b
}
foo("a", 2);
foo("a");
One of the limitations of this approach is that it doesn't work if you have two optio...