Applied Programming/Files/Python3
files.py
edit"""This program demonstrates file processing.
It creates a file, adds data to the file, displays the file, appends more data
to the file, displays the file, and then deletes the file.
It will not run if the file already exists.
Input:
None
Output:
A temporary file and file contents.
References:
None
"""
import os
import sys
def create_file(filename):
"""Creates filename and adds temperature data to the file.
Args:
filename (string): Filename to create.
Returns:
None
"""
with open(filename, "w") as file:
file.write("C\tF\n")
for c in range(0, 51):
f = c * 9 / 5 + 32
file.write("%.1f\t%.1f\n" % (c, f))
def read_file(filename):
"""Reads filename and displays each line.
Args:
filename (string): Filename to open and read.
Returns:
None
"""
with open(filename, "r") as file:
for line in file:
line = line.strip()
print(line)
print("")
def append_file(filename):
"""Appends temperature data to filename.
Args:
filename (string): Filename to open and append.
Returns:
None
"""
with open(filename, "a") as file:
for c in range(51, 101):
f = c * 9 / 5 + 32
file.write("%.1f\t%.1f\n" % (c, f))
def delete_file(filename):
"""Deletes filename.
Args:
filename (string): Filename to delete.
Returns:
None
"""
os.remove(filename)
def main():
"""Runs the main program logic."""
try:
filename = "~file.txt"
if os.path.isfile(filename):
print("File '%s' already exists." % filename)
exit(1)
create_file(filename)
read_file(filename)
append_file(filename)
read_file(filename)
delete_file(filename)
except:
print("Unexpected error.")
print("Error:", sys.exc_info()[1])
print("File: ", sys.exc_info()[2].tb_frame.f_code.co_filename)
print("Line: ", sys.exc_info()[2].tb_lineno)
main()
binary_file.py
editBinary files are usually thought of as being a sequence of bytes, which means the binary digits (bits) are grouped in eights. Binary files typically contain bytes that are intended to be interpreted as something other than text characters. Compiled computer programs are typical examples; indeed, compiled applications are sometimes referred to, particularly by programmers, as binaries. But binary files can also mean that they contain images, sounds, compressed versions of other files, etc.—in short, any type of file content whatsoever.[1]
"""This program demonstrates binary file creation
It creates a file and adds data to the file
Input: None
Output:
upper_characters: file with the upper case english letters
lower_characters: file with the lower case english letters
References:
* https://stackoverflow.com/questions/82831/how-do-i-check-whether-a-file-exists-without-exceptions
* https://en.wikipedia.org/wiki/Binary_file
* https://www.youtube.com/watch?v=le0Bo3K-bks
"""
import sys
import struct
def get_file_name():
"""Obtains user input for file name
Input: None
Returns:
filename: string
Except:
ValueError: If filename is not a valid string
Exit:
filename is empty
"""
try:
print('Please input the file name you would like to use. To exit, press Enter')
filename = input()
if type(filename) is not str:
raise ValueError
if filename == '':
sys.exit(0)
else:
return filename
except ValueError:
print("File name must be a string.")
print("ValueError: '%s' is invalid." % filename)
def append_characters(filename):
"""Fills filename with the upper case english alphabet characters
Input:
filename: string
Output: None
Exits:
ValueError: If filename is not a valid string
ValueError: If filename is an empty string
"""
try:
fd_out = open(filename, "wb")
if type(filename) is not str:
raise ValueError("File name must be a string.\nReceived %f" % filename)
if filename == '':
raise ValueError("File name cannot be empty.")
id = 65
val = id
for i in range(26):
entry = struct.pack('<HI', id, val)
id += 1
val = id
fd_out.write(entry)
fd_out.flush()
fd_out.close()
except:
print("Unexpected error.")
print("Error:", sys.exc_info()[1])
print("File: ", sys.exc_info()[2].tb_frame.f_code.co_filename)
print("Line: ", sys.exc_info()[2].tb_lineno)
def main():
"""Runs the main program logic."""
try:
filename = get_file_name()
append_characters(filename)
except:
print("Unexpected error.")
print("Error:", sys.exc_info()[1])
print("File: ", sys.exc_info()[2].tb_frame.f_code.co_filename)
print("Line: ", sys.exc_info()[2].tb_lineno)
if __name__ == "__main__":
main()
How to view file
editThis command is the same for both Windows and UNIX based systems.
> hexdump -C "filename"
Try It
editCopy and paste the code above into one of the following free online development environments or use your own Python3 compiler / interpreter / IDE.
See Also
edit- Computer Programming
- Python Programming
- Wikibooks: Python Programming
- Wikibooks: Non-Programmer's Tutorial for Python 3
- ↑ "Binary file". Wikipedia. 2018-12-30. https://en.wikipedia.org/w/index.php?title=Binary_file&oldid=876032410.