During program execution, we often want to create data that is not needed after the program exits. Temporary files and directories are useful for this purpose because they do not pollute the file system over time.
4 snippets
import json
import os
import uuid
filename = str(uuid.uuid4()) # create random file name
# JSON data to be written
jsonDict ={
"firstname" : "John",
"lastname" : "Doe",
"age" : 30,
"phonenumber" : "9976770500"
}
# write JSON to file
with open(filename, "w") as f:
json.dump(jsonDict, f)
# read JSON string from file
f = open(filename, "r")
print(f.read())
f.close()
os.remove(filename)
# Output:
# {"firstname": "John", "lastname": "Doe", "age": 30, "phonenumber": "9976770500"}
You can write JSON to a file using the json.dump() function from the JSON module combined with file handling in Python. In thisexample, we open a file in writing mode. If the file doesn't exist, it will be created. The json.dump() function converts the Python dictionary into a JSON string, which is then saved in the file.
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import os
import uuid
filename = str(uuid.uuid4()) # create random file name
wLines = ["First line\n", "Second line\n", "Third line\n"]
# writing lines to file
f = open(filename, 'w')
f.writelines(wLines)
f.close()
#--------------------------------------------------------#
print("-----Read lines using 'readlines' method-----")
f = open(filename, 'r')
rLines = f.readlines()
for lineNumber, line in enumerate(rLines, 1):
print("Line {}: {}".format(lineNumber, line.strip()))
#--------------------------------------------------------#
print("-----Read lines using 'readline' method-----")
f = open(filename, 'r')
lineNumber = 1
while True:
lineNumber += 1
# Get next line from file
line = f.readline()
# if line is empty
# end of file is reached
if not line:
break
print("Line {}: {}".format(lineNumber, line.strip()))
f.close()
#--------------------------------------------------------#
print("-----Read lines via file object iteration-----")
f = open(filename, 'r')
for lineNumber, line in enumerate(f, 1):
print("Line {}: {}".format(lineNumber, line.strip()))
#--------------------------------------------------------#
print("-----Read lines via file contex manager-----")
with open(filename, "r") as f:
for lineNumber, line in enumerate(f, 1):
print("Line {}: {}".format(lineNumber, line.strip()))
os.remove(filename) # remove file
# Output example:
# Read lines using 'readlines' method
# Line 1: First line
# Line 2: Second line
# Line 3: Third line
Here's an example of reading from a file line by line in Python.
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package main
import (
"bufio"
"fmt"
"os"
)
func checkErr(err error) {
if err != nil {
panic(err)
}
}
func main() {
content := "Some content"
// write a string (or just bytes) into a file
err := os.WriteFile("/tmp/dfile1", []byte(content), 0644)
checkErr(err)
// open a file for writing
file, err := os.Create("/tmp/dfile2")
checkErr(err)
// defer a Close immediately after opening a file
defer file.Close()
bytesCount, err := file.Write([]byte(content))
checkErr(err)
fmt.Printf("wrote %d bytes\n", bytesCount)
bytesCount, err = file.WriteString("Some other content\n")
checkErr(err)
fmt.Printf("wrote %d bytes\n", bytesCount)
// flush writes to a stable storage (file system for example)
file.Sync()
// bufio provides buffered writers
writer := bufio.NewWriter(file)
bytesCount, err = writer.WriteString("Some othe buffered content\n")
checkErr(err)
fmt.Printf("wrote %d bytes\n", bytesCount)
// ensure all buffered operations have been applied to the underlying writer
writer.Flush()
}
Here are examples of writing data to files using Go.
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