CODEWITHSUNDEEP
pythonstringoptimization
Anil Purohit
Anil Purohit

Reputation: 186

Optimised way of string operation in Python

Given a string and an integer. Operations is, append integer to string of 4 zeros and get the last 4 characters of the result string. which one of the below two approaches is a better approach in terms of optimisation and readability for this? If there exits any other suggest me that as well.

result_str = ("0000" + str(integer_value))[-4:]

or

result_str = "%04d" % integer_value

0 <= integer_value <=999

Upvotes: 0

Views: 78

Answers (3)

Alex Reynolds
Alex Reynolds

Reputation: 96947

Use timeit to figure which is most efficient for your version of Python.

Here's an example of timing results for your methods and other methods proposed in other answers:

$ python
Python 2.7.6 (default, Sep  9 2014, 15:04:36) 
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import timeit
>>> s1 = "(\"0000\" + str(123))[-4:]"
>>> timeit.timeit(stmt=s1, number=1000000)
0.26563405990600586
>>> s2 = "\"%04d\" % 123"
>>> timeit.timeit(stmt=s2, number=1000000)
0.021093130111694336
>>> s3 = "str(123).zfill(4)"
>>> timeit.timeit(stmt=s3, number=1000000)
0.3430290222167969
>>> s4 = "'{0:0>4}'.format(123)"
>>> timeit.timeit(stmt=s4, number=1000000)
0.3574531078338623

This suggests that the following works fastest among the suggested options:

result_str = "%04d" % integer_value

Whether a 10-fold speedup is trivial or non-trivial will likely depend on your use case.

From a readability standpoint, this last option is the most familiar to me, given experience with C and Perl. I would find this more readable than any of the other more Python-specific options.

Upvotes: 1

H&#229;ken Lid
H&#229;ken Lid

Reputation: 23064

I prefer str.format() which is more flexible than string formatting with %

>>> '{0:0>4}'.format(8)
'0008'

Upvotes: 2

TehTris
TehTris

Reputation: 3217

>>> some_number = 8
>>> str(some_number).zfill(4)
'0008'

zfill automatically adds leading zeros to the front of a string, turning the entire string into that long

>>> 'pie'.zfill(4)
'0pie'
>>> ':)'.zfill(5)
'000:)'

Upvotes: 1

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