How to extract allel, Genotype from vcf file using python or other language for 23GB files?
Well, I am able to right script to get allel but for large VCF file its difficult ? what should other possible way to get allel, Genotype information?
Extracting genotype information using R.

    library(vcfR)
    vcf <- read.vcfR(vcf_file, verbose = FALSE )
    gt <- extract.gt(vcf, element = c('GT'), as.numeric = TRUE)

For python take a look at the following article.

http://alimanfoo.github.io/2017/06/14/read-vcf.html

Genotypes can also be extracted using `SnpSift.jar` in [snpEff][1] using the following command.

    java -jar ../snpEff/SnpSift.jar extractFields annotated.vcf   CHROM POS REF ALT  "GEN[*].GT" > output.tsv


  [1]: http://snpeff.sourceforge.net/