Step-by-Step Guide: Reading Tuples from Files in Python
Python has a built-in capability to read and write tuples from files. Tuples are a sequence of immutable Python objects, enclosed in parentheses. They are useful for grouping related data that should not be modified. This guide will take you through the steps involved in reading tuples from files in Python.
Step 1: Open the File
The first step in reading tuples from a file in Python is to open the file. You can use Python’s built-in open() function to open a file. In the following code, we will open a file called «example.txt» in read mode using the open() function:
In this code, «example.txt» is the name of the file, and «r» tells Python that we want to open it in read mode.
Step 2: Read the File
Once the file is open, we can read it using the read() method. In the case of tuples, we assume that each line of the file contains a single tuple. We can read the file one line at a time as follows:
for line in file: print(line) In this code, we are using a for loop to iterate through each line of the file. Each line of the file is represented as a string in Python.
Step 3: Convert the String to a Tuple
Once we have read a line from the file, we can convert the string to a tuple. We can use Python’s built-in eval() function to evaluate the string as a Python expression. The expression should evaluate to a tuple.
for line in file: tuple = eval(line) print(tuple) In this code, we are using the eval() function to convert each line of the file into a tuple. The print() function is then used to print the tuple to the console.
Step 4: Close the File
Once we have finished reading the file, we should close it using the close() method.
In this code, we are using the close() method to close the file.
Conclusion
In this article, we have shown you how to read tuples from files in Python. We used Python’s built-in open() , read() , eval() , and close() functions to read the file, convert each line to a tuple, and close the file. With this guide, you should now be able to read tuples from files in Python with ease.
Binary files. Examples of working with binary files
This topic shows how you can save data in binary files without using the standard pickle or struct modules.
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1. The concept of binary files. Presentation of information in binary files
Python has tools for working with binary files. Binary files use strings of type bytes. This means when reading binary data from a file, an object of type bytes is returned.
The binary file is opened using the open() function, whose mode parameter contains the character ‘b’ . More details about opening/closing binary files are described here .
Unlike text files, binary files do not convert characters to the end of the string ‘\n’ .
An example demonstrating the features of the presentation of information in binary files.
# Python. Work with binary files # Open binary file for reading f = open('myfile1.bin', 'rb') # Get a string from binary file d = f.read() # Display this string. # The output will be as a string of characters print("d color: #ff0000;"># d = b'\x80\x03]q\x00(K\x01\x88G@\x07\n=p\xa3\xd7\ne.' # If print as a separate character, # then the character code will be displayed - as an integer print("d[5] color: #ff0000;"># d[5] = 40 print("d[0] color: #ff0000;"># d[0] = 128 # Use bin function for single character print(bin(d[2])) # 0b1011101 f.close()
The result of the program
d = b'\x80\x03]q\x00(K\x01\x88G@\x07\n=p\xa3\xd7\ne.' d[5] = 40 d[0] = 128 0b1011101
Based on the example above, the following conclusions can be drawn:
- a string of binary data is output as a string;
- a single character (element) of binary data is represented as 8-bit integers.
2. Writing / reading a list that contains real numbers. Example
# Binary files Writing / reading a list of real numbers # 1. Given list of real numbers L = [1.5, 2.8, 3.3] # 2. File writing # 2.1. Open file for writing f = open('myfile3.bin', 'wb') # 2.2. Bypass list and write data to a file for item in L: # add the character '\ n' so that numbers can be recognized s = str(item) + '\n' # Encode () method - converts a string to a sequence of bytes bt = s.encode() f.write(bt) # write() method - write to file # 2.3. Close file f.close(); # 3. Read list from binary file 'myfile3.bin' # 3.1. Create an empty list L2 = [] # 3.2. Open file for reading f = open('myfile3.bin', 'rb') # 3.3. Bypass lines of a file, converting and adding to the list L2 for ln in f: x = float(ln) # get a number L2 = L2 + [x] # Add number to list # 3.4. Output the list print("L2 color: #ff0000;"># L2 = [1.5, 2.8, 3.3] # 3.5. Close file f.close();
The result of the program
3. Writing/reading a tuple containing character strings. Example
In this example, the character strings in the binary file are separated by the character ‘\n’ . Thus, it is possible to write and read information without losing its structure.
# Binary files. Writing / reading a tuple containing character strings # 1. The specified tuple with strings T = ( 'abc', 'def', 'ghi', 'jk lmn') # 2. Write tuple T to file 'myfile5.bin' # 2.1. Open file for writing f = open('myfile5.bin', 'wb') # 2.2. Tuple bypass cycle for item in T: bt = (item + '\n').encode() # convert (str + '\n') => bytes f.write(bt) # write bt to file # 2.3. Close file f.close(); # 3. Read tuple from binary file 'myfile5.bin' # 3.1. Open file for reading f = open('myfile5.bin', 'rb') # 3.2. A new tuple T2 = () # 3.3. Read data from file for line in f: s = line.decode() # convert bytes=>str s = s[:-1] # Remove the last character T2 = T2 + (s,) # Add string s to tuple # 3.4. Print the tuple print("T2 color: #ff0000;"># 3.5. Close file f.close();
The result of the program
4. Writing / reading a set containing real numbers. Example
A set that contains only objects of the same type can be written to a file. In this example, many real numbers are written.
# Binary files. Writing/reading a set that contains real numbers # 1. Given set M = < 0.2, 0.3, 0.8, 1.2, 1.77 ># 2. Writing the set M to the file 'myfile6.bin' # 2.1. Open file for writing f = open('myfile6.bin', 'wb') # 2.2. The loop of bypass the set for item in M: s = str(item) + '\n' # convert float=>str + '\n' bt = s.encode() # convert str=>bytes f.write(bt) # write bt to file # 2.3. Close file f.close(); # 3. Read set from binary file 'myfile6.bin' # 3.1. Open file for reading f = open('myfile6.bin', 'rb') # 3.2. Create a new set M2 = set() # 3.3. Read data from file for line in f: x = float(line) # convert bytes=>x M2 = M2.union() # add x to the set # 3.4. Print the set print("M2 color: #ff0000;"># 3.5. Close file f.close()
The result of the program
The content of myfile6.bin file
5. Writing/reading a two-dimensional matrix of rows of a given size. Example
In the example, the matrix is presented in the form of a list.
# Binary files. Writing/reading a matrix that contains rows # 1. Given matrix of rows 3*4 in size MATRIX = [ [ 'aa', 'ab', 'ac', 'ad'], [ 'ba', 'bb', 'bc', 'bd'], [ 'ca', 'cb', 'cc', 'cd'] ] # 2. Writing MATRIX matrix to the file 'myfile7.bin' # 2.1. Open file for writing f = open('myfile7.bin', 'wb') # 2.2. First, write the size of the matrix m = 3 n = 4 # convert m, n to str type sm = str(m) + '\n' sn = str(n) + '\n' # convert str to bytes bm = sm.encode() bn = sn.encode() # write matrix sizes to file f.write(bm) f.write(bn) # 2.3. The loop of matrix traversal for row in MATRIX: # here you just need to write lines with the character '\n' for item in row: item = item + '\n' bt = item.encode() # str=>bytes f.write(bt) # write bt to file # 2.3. Close file f.close(); # 3. Read matrix from binary file 'myfile7.bin' # 3.1. Open file for reading f = open('myfile7.bin', 'rb') # 3.2. A new matrix MATRIX2 = [] # 3.3. Read data from file # 3.3.1. First, read size s = f.readline() m2 = int(s) s = f.readline() n2 = int(s) # 3.3.2. Loop of reading the lines and the creation of a matrix size m2*n2 i = 0 while i < m2: # m2 rows in matrix row = [] # one row in list j = 0 while j < n2: bs = f.readline() # read one element of type bytes s = bs.decode() # convert bytes=>str s = s[:-1] # remove '\n' row += [s] # add to the list j = j+1 MATRIX2 += [row] # add one row of the list to the matrix i = i+1 # 3.4. Display new matrix i = 0 while i < m2: print("MATRIX2[", i, "] color: #ff0000;"># 3.5. Close file f.close()
The result of the program
MATRIX2[ 0 ] = ['aa', 'ab', 'ac', 'ad'] MATRIX2[ 1 ] = ['ba', 'bb', 'bc', 'bd'] MATRIX2[ 2 ] = ['ca', 'cb', 'cc', 'cd']
The content of file myfile7.txt
3 4 aa ab ac ad ba bb bc bd ca cb cc cd
6. Writing/reading a dictionary. Example
Let some dictionary be given that needs to be written to a binary file.
# Binary files. Writing/reading a dictionary # 1. The specified dictionary. Pairs of type str:int D = < 'One':1, 'Two':2, 'Three':3, 'Four':4 > # 2. Writing D dictionary to file 'myfile8.bin' # 2.1. Open file for writing f = open('myfile8.bin', 'wb') for key in D: # dictionary bypass # get the value value = DPython read tuple from file # Write sequentially key, then value svalue = str(value) + '\n' # convert value to string skey = key + '\n' # add '\n' to key string # Convert key:svalue from string to bytes b_key = skey.encode() b_svalue = svalue.encode() # write b_key, b_svalue to the file f.write(b_key) f.write(b_svalue) # 2.3. Close file f.close(); # 3. Read dictionary from binary file 'myfile8.bin' # 3.1. Open file for reading f = open('myfile8.bin', 'rb') # 3.2. New dictionary to be read from file D2 = dict() # 3.3. Read the whole file at once b_strings = f.readlines() # b_strings - list of strings of type bytes # 3.4. Bypass the b_strings list. # The key is read first, then the value, etc. fkey = True # if True, then the key is read, otherwise the value is read for item in b_strings: if fkey: # check if key is read skey = item.decode() # convert bytes=>str key = skey[:-1] # remove '\n' fkey = False else: svalue = item.decode() # convert bytes=>str value = int(svalue) # convert str=>int D2Python read tuple from file = value # add to dictionary fkey = True # indicate that the next iteration will be the key # 3.5. Output the dictionary print("D2 color: #ff0000;"># 3.6. Close file f.close()
The result of the program
The content of myfile8.txt file
One 1 Two 2 Three 3 Four 4
7. Copying one binary file to another
# Binary files. Copying files # 1. Open the files f1 = open('myfile8.bin', 'rb') # file - source, it is opened for reading f2 = open('copyfile8.bin', 'wb') # file - copy # 2. Read file f1 to bstrings string list bstrings = f1.readlines() # 3. Write bstrings string list to f2 file f2.writelines(bstrings) # 4. Close the files f1.close() f2.close()
8. Combining two binary files. Example
The example implements the operation of combining two files into the resulting third file. First, data from source files is read into lists. Then, these lists are concatenated and the resulting list is written to the result file.
# Combining files myfile1.bin+myfile2.bin => myfile3.bin # 1. Open files to read f1 = open('myfile1.bin', 'rb') f2 = open('myfile2.bin', 'rb') # 2. Read files into L1, L2 lists L1 = f1.readlines() L2 = f2.readlines() # 3. Combine lists L3 = L1 + L2 # 4. Close files myfile1.bin, myfile2.bin f1.close() f2.close() # 5. Open file myfile3.bin to write f3 = open('myfile3.bin', 'wb') # 6. Write list L3 into the file f3.writelines(L3) # 7. Close the result file f3.close()