Python-based File Operation
A Python-based File Operation is a file operation that is a Python operation.
- Context:
- It can range from being a Python File Open Operation to being a Python File Close Operation (on Python file descriptors).
- It can range from being a Python File Read Operation to being a Python File Write Operation (such as a Python file append operation).
- It can range from being a Python File Metadata Operation.
- Example(s):
with open('testit.txt', encoding="utf8") as f:
inputFileText = f.read()
mylist = f.read().splitlines()
print(inputFileText)
mylist[0:10]infile = open('file.csv', encoding="utf8")
data_list = [line.rstrip().split(',') for line in infile.readlines()]allFiles = glob.glob("./*.csv.zip")
- a Pandas-based File Operation, such as:
df = pandas.read_csv("./file.csv.zip", compression='zip', header=0, sep=',', quotechar='"', skiprows=0) ;
pandas_df.to_csv("out.tsv", sep='\t', index=True, cols=["col3","col1"], encoding='utf-8') ;
- …
- Counter-Example(s):
- See: Python Coding Example.
References
2014
- http://en.wikibooks.org/wiki/Python_Programming/Files
- Files, specifically file handles, are an important example of resources, and thus should generally be managed using the
with
statement; see context managers section.In rare cases – namely when a file is not only used within a single block of code – it is necessary to do manual resource management using
File.close()
, but this is error-prone and requires great care to be exception safe. In interactive use using explicitopen()
andFile.close()
results in immediate evaluation, instead of the delayed evaluation of using awith
statement.
- Files, specifically file handles, are an important example of resources, and thus should generally be managed using the
Examples
- Reading & Writing Files
Just reading from a file
open my $io, “<-" or die "NO STDIN: $!" ;
Mixed Read & Write
...
- Subroutine-based
Subroutine to open a file for writing and write into it.
import csv filename = sys.argv[1] with open(filename, 'rb') if sys.argv[1] is not "-" else sys.stdin as f: reader = csv.reader(f,dialect="excel-tab") # creates the reader object for row in reader: ...
Subroutine to open a file for writing and write into it.
...
- File Open Codes
...
- File Management
Rename a File
...
Delete a file
...
Choose between STDIN or file
...
- Directory-based operations
Read a directory's files (shortcut with pattern matching).
...
Load all files in a directory into the @files array
...
a subroutine approach
...
- JSON-based operations
import json with open("data_file.json", "w") as write_file: json.dump(data, write_file) print(json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=4)) { "4": 5, "6": 7 } ...