Initialise a list to a specific length in Python

Question

How do I initialise a list with 10 times a default value in Python   I m searching for a good-looking way to initialize a empty list with a specific range   So make a list that contains 10 zeros or something to be sure that my list has a specific length

User · Answer

In a talk about core containers internals in Python at PyCon 2012, Raymond Hettinger is suggesting to use [None] * n to pre-allocate the length you want.

Slides available as PPT or via Google

The whole slide deck is quite interesting. The presentation is available on YouTube, but it doesn't add much to the slides.

User · Answer

list multiplication works    gt  gt  gt   0    10  0  0  0  0  0  0  0  0  0  0

User · Answer

If the  default value  you want is immutable   eduffy s suggestion  e g   0  10  is good enough   But if you want  say  a list of ten dicts  do not use      10 -- that would give you a list with the same initially-empty dict ten times  not ten distinct ones  Rather  use     for i in range 10   or similar constructs  to construct ten separate dicts to make up your list

[python] Initialise a list to a specific length in Python

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