The error ValueError: zero length field name in format occurs when using implicit positional arguments in .format() strings with Python versions that don’t support this syntax. The Problematic Code print(‘== {} SPF’.format(d)) This raises ValueError: zero length field name in format on older Python interpreters. Why This Happens The {} syntax without explicit position numbers…
BAM files store aligned sequence reads in a compressed binary format. Counting reads by chromosome is a common task in genomics workflows—useful for quality control, coverage analysis, and identifying potential sequencing biases. Using samtools idxstats The fastest and most straightforward approach is samtools idxstats, which requires an indexed BAM file: samtools index reads.bam samtools idxstats…
By default, print() writes to STDOUT. Both STDOUT and STDERR go to your terminal unless you redirect them. Here’s how to send output to each stream explicitly. Printing to STDOUT The standard print() function writes to STDOUT and automatically adds a newline: print(“your message”) Printing to STDERR To print to STDERR, pass the file parameter:…
To get the parent process ID (PPID) of the running process, use the os.getppid() function: import os ppid = os.getppid() print(f”Parent Process ID: {ppid}”) This returns the process ID of the parent process as an integer. On Unix-like systems, this is straightforward. On Windows, the behavior is consistent as well. Accessing Full Process Information For…
The process ID (PID) is essential for logging, creating lock files, inter-process communication, and debugging. Knowing how to reliably retrieve it matters in production systems. Basic Usage The simplest way to get your process’s own PID is through the os module: import os print(os.getpid()) This returns an integer representing the current process ID. It’s lightweight…
Bash doesn’t have a built-in split function, but you can achieve string splitting through several methods. The most common approach uses IFS (Internal Field Separator), though other techniques exist depending on your needs. IFS with read The simplest method for splitting a string by a delimiter: string=”apple,banana,cherry” IFS=’,’ read -ra ADDR <<< “$string” for i…
Retrieving the hostname of the machine running your script is essential for logging, node identification in distributed systems, monitoring, and conditional logic based on where code executes. Bash offers multiple approaches with different tradeoffs. Using the $HOSTNAME Variable The quickest method is the $HOSTNAME environment variable, which Bash sets at shell initialization: echo $HOSTNAME host01…
There are several ways to retrieve the hostname of the current machine in Python, each with different use cases. Using socket.gethostname() The simplest and most common approach is the socket module, which is part of Python’s standard library: import socket hostname = socket.gethostname() print(hostname) This returns the hostname as a string. On most systems, this…
Epoch timestamps (seconds since January 1, 1970 UTC) are common in logs, databases, and APIs. Python’s datetime module handles conversion cleanly. Basic Conversion The simplest approach uses datetime.fromtimestamp(): from datetime import datetime epoch = 1609459200 dt = datetime.fromtimestamp(epoch) print(dt) # 2021-01-01 00:00:00 For UTC times specifically, use utcfromtimestamp(): from datetime import datetime, timezone epoch =…
Python offers several ways to get the current epoch timestamp, each suited to different use cases. The choice depends on your precision requirements and whether you’re working with timezone-aware operations. Using time.time() The simplest approach is time.time(), which returns the current time as a float representing seconds since the Unix epoch (January 1, 1970, 00:00:00…
Environment variables are essential for configuration management—API keys, database URLs, feature flags, and environment-specific settings should never be hardcoded. Python provides straightforward mechanisms to access them. The os Module The standard way to read environment variables is with the os module: import os api_key = os.environ[‘API_KEY’] This raises a KeyError if the variable doesn’t exist….
Java has several solid REPL implementations available. Here are the main options and how to use them. jshell (Official) The best choice for most users is jshell, included in JDK 9+. It’s the official interactive shell for Java and comes with every modern Java installation. Start it immediately: jshell Basic usage: jshell> long ts =…
There are several ways to retrieve the hostname on a Linux system from Python. The choice depends on your use case and whether you need the simple hostname or the fully qualified domain name (FQDN). Using socket.gethostname() The simplest approach uses the socket module from the standard library: import socket hostname = socket.gethostname() print(hostname) This…
Reading a file line by line is memory-efficient and the standard approach for handling large text files in Python. The key is choosing the right method for your use case. The Iterator Approach (Recommended for Large Files) For most scenarios, especially with large files, use the file object as an iterator: with open(‘file.txt’, ‘r’) as…
The most straightforward way to read an environment variable in Python is with os.getenv(): import os api_key = os.getenv(‘API_KEY’) print(api_key) If the variable doesn’t exist, getenv() returns None. You can provide a default value as a fallback: debug_mode = os.getenv(‘DEBUG’, ‘False’) port = os.getenv(‘PORT’, ‘8000’) For variables that must exist, use os.environ[] instead. This raises…
There are several ways to get a file’s size without importing the os module. Each approach has different use cases depending on your needs. Using pathlib.Path The most straightforward approach uses pathlib, which is part of the standard library: from pathlib import Path file_path = Path(‘example.txt’) size = file_path.stat().st_size print(f”File size: {size} bytes”) This is…
The most straightforward approach is os.access(), which tests whether the process has the requested access to a file: import os file_path = “example.txt” # Check if file is readable if os.access(file_path, os.R_OK): print(“File is readable”) # Check if file is writable if os.access(file_path, os.W_OK): print(“File is writable”) # Check if file exists and is executable…
The most direct way to check for key existence is the in operator: if ‘key’ in my_dict: print(“Key exists”) This is O(1) average case and the idiomatic Python approach. It’s fast and readable. Alternatives Based on Your Use Case Using dict.get() when you need the value: value = my_dict.get(‘key’) if value is not None: print(f”Key…
Python provides several ways to check if files or directories exist, with different trade-offs depending on your use case. Using pathlib (recommended) The modern approach uses pathlib.Path, which is cleaner and more object-oriented: from pathlib import Path path = Path(‘/etc/passwd’) # Check if path exists (file or directory) if path.exists(): print(“Path exists”) # Check if…
Vim’s filetype detection usually works automatically, but sometimes you need to manually override or set the filetype for a specific buffer. This guide covers manual filetype setting, debugging detection issues, and creating custom filetype definitions. Set Filetype Manually :set filetype=python Or use the shorthand: :set ft=python This immediately applies the syntax highlighting, indentation rules, and…