Menu
Every so often on here I see someone's code and what looks to be a 'one-liner', that being a one line statement that performs in the standard way a traditional 'if' statement or 'for' loop works.
I've googled around and can't really find what kind of ones you can perform? Can anyone advise and preferably give some examples?
For example, could I do this in one line:
example = "example" if "exam" in example: print "yes!" Or:
for a in someList: list.append(splitColon.split(a)) 
683
Only use single-line if statements on a single line While the compiler sees this as one statement guarded by a single condition, humans often accidentally read this is an if block, whether there are curly braces or not, thanks to the indentation. Humans notice the indentation, the compiler does not.
Python If Statement In One LineIn Python, we can write “if” statements, “if-else” statements and “elif” statements in one line without worrying about the indentation. In Python, it is permissible to write the above block in one line, which is similar to the above block.
The recommended style for multiline if statements in Python is to use parenthesis to break up the if statement. The PEP8 style guide recommends the use of parenthesis over backslashes and putting line breaks after the boolean and and or operators. Copied!
These statements can very well be written in one line by putting semicolon in between. However, this practice is not allowed if there is a nested block of statements.
Well,
if "exam" in "example": print "yes!" Is this an improvement? No. You could even add more statements to the body of the if-clause by separating them with a semicolon. I recommend against that though.
97
I've found that in the majority of cases doing block clauses on one line is a bad idea.
It will, again as a generality, reduce the quality of the form of the code. High quality code form is a key language feature for python.
In some cases python will offer ways todo things on one line that are definitely more pythonic. Things such as what Nick D mentioned with the list comprehension:
newlist = [splitColon.split(a) for a in someList] although unless you need a reusable list specifically you may want to consider using a generator instead
listgen = (splitColon.split(a) for a in someList) note the biggest difference between the two is that you can't reiterate over a generator, but it is more efficient to use.
There is also a built in ternary operator in modern versions of python that allow you to do things like
string_to_print = "yes!" if "exam" in "example" else "" print string_to_print or
iterator = max_value if iterator > max_value else iterator Some people may find these more readable and usable than the similar if (condition): block.
When it comes down to it, it's about code style and what's the standard with the team you're working on. That's the most important, but in general, i'd advise against one line blocks as the form of the code in python is so very important.
29
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
