While Loops

1 min read • Verified October 2026 • Peer-Reviewed Learning Resource

Tested Stacks: GATK 4.6.1 Samtools 1.21 Nextflow 24.10 Seurat v5.1 Python 3.12

Prerequisites: Basic Linux CLI & Sequencing Formats

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While loop execute a block of code as long as a specified condition is true.

Pyton

				# Example: Running an experiment until a specific result is achieved
experiment_result = 0

while experiment_result < 100:
    print("Running experiment...")
    # Your experiment code here
    experiment_result += 10

print("Experiment Done")

# Example: Running an experiment until a specific result is achieved
experiment_result = 0

while experiment_result < 100:
    print("Running experiment...")
    # Your experiment code here
    experiment_result += 10

print("Experiment Done")

The output will be
Running experiment…
Running experiment…
Running experiment…
Running experiment…
Running experiment…
Running experiment…
Running experiment…
Running experiment…
Running experiment…
Running experiment…

Experiment Done

The loop continues until the condition (experiment_result < 100) becomes false

⚠️

Common Pitfalls & Troubleshooting Checklist

Java Heap Exhaustion (GATK / Picard): If processes terminate with java.lang.OutOfMemoryError, set your environment variable explicitly: export _JAVA_OPTIONS="-Xmx16g -Djava.io.tmpdir=/tmp".
Index Timestamp Mismatch: If tools complain that a BAM index is missing or out of date, regenerate with samtools index -@ 4 sample.bam.
Conda Channel Conflicts: Avoid ABI incompatibilities between bioconda and conda-forge by setting strict priority: conda config --set channel_priority strict.
Chromosome Naming Contamination: Always verify whether reference FASTA headers use chr1 or 1; divergent naming causes silent alignment drops.

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