Does reading an entire file leave the file handle open

Question

If you read an entire file with content   open  Path to file    r   read   is the file handle left open until the script exits   Is there a more concise method to read a whole file

User · Answer

Well  if you have to read file line by line to work with each line  you can use  with open  Path to file    r   as f      s   f readline       while s            do whatever you want to         s   f readline     Or even better way   with open  Path to file   as f      for line in f            do whatever you want to

User · Answer

Instead of retrieving the file content as a single string  it can be handy to store the content as a list of all lines the file comprises   with open  Path to file    r   as content file      content list   content file read   strip   split   n     As can be seen  one needs to add the concatenated methods  strip   split   n   to the main answer in this thread   Here   strip   just removes whitespace and newline characters at the endings of the entire file string  and  split   n   produces the actual list via splitting the entire file string at every newline character  n   Moreover  this way the entire file content can be stored in a variable  which might be desired in some cases  instead of looping over the file line by line as pointed out in this previous answer

User · Answer

The answer to that question depends somewhat on the particular Python implementation     To understand what this is all about  pay particular attention to the actual file object   In your code  that object is mentioned only once  in an expression  and becomes inaccessible immediately after the read   call returns   This means that the file object is garbage   The only remaining question is  When will the garbage collector collect the file object     in CPython  which uses a reference counter  this kind of garbage is noticed immediately  and so it will be collected immediately   This is not generally true of other python implementations   A better solution  to make sure that the file is closed  is this pattern   with open  Path to file    r   as content file      content   content file read     which will always close the file immediately after the block ends  even if an exception occurs   Edit   To put a finer point on it   Other than file   exit      which is  automatically  called in a with context manager setting  the only other way that file close   is automatically called  that is  other than explicitly calling it yourself   is via file   del       This leads us to the question of when does   del     get called      A correctly-written program cannot assume that finalizers will ever run at any point prior to program termination    -- https   devblogs microsoft com oldnewthing 20100809-00  p 13203  In particular      Objects are never explicitly destroyed  however  when they become unreachable they may be garbage-collected  An implementation is allowed to postpone garbage collection or omit it altogether     it is a matter of implementation quality how garbage collection is implemented  as long as no objects are collected that are still reachable                  CPython currently uses a reference-counting scheme with  optional  delayed detection of cyclically linked garbage  which collects most objects as soon as they become unreachable  but is not guaranteed to collect garbage containing circular references    -- https   docs python org 3 5 reference datamodel html objects-values-and-types   Emphasis mine   but as it suggests  other implementations may have other behavior   As an example  PyPy has 6 different garbage collection implementations

User · Answer

You can use pathlib   For Python 3 5 and above   from pathlib import Path contents   Path file path  read text     For older versions of Python use pathlib2     pip install pathlib2   Then   from pathlib2 import Path contents   Path file path  read text       This is the actual read text implementation   def read text self  encoding None  errors None               Open the file in text mode  read it  and close the file              with self open mode  r   encoding encoding  errors errors  as f          return f read

[python] Does reading an entire file leave the file handle open?

Examples related to python

Examples related to file-io

Examples related to filehandle