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The animal on the cover of Test-Driven Development with Python is a cashmere goat. Though all goats can produce a cashmere undercoat, only those goats selectively bred to produce cashmere in commercially viable amounts are typically considered “cashmere goats.” Cashmere goats thus belong to the domestic goat species Capra hircus.

The exceptionally fine, soft hair of the undercoat of a cashmere goat grows alongside an outer coat of coarser hair as part of the goat’s double fleece. The cashmere undercoat appears in winter to supplement the protection offered by the outer coat, called guard hair. The crimped quality of cashmere hair in the undercoat accounts for its lightweight yet effective insulation properties.

The name “cashmere” is derived from the Kashmir Valley region on the Indian subcontinent where the textile has been manufactured for thousands of years. A diminishing population of cashmere goats in modern Kashmir has led to the cessation of exports of cashmere fiber from the area. Most cashmere wool now originates in Afghanistan, Iran, Outer Mongolia, India, and—predominantly—China.

Cashmere goats grow hair of varying colors and color combinations. Both males and females have horns, which serve to keep the animals cool in summer and provide the goats’ owners with effective handles during farming activities.

Many of the animals on O’Reilly covers are endangered; all of them are important to the world. To learn more about how you can help, go to animals.oreilly.com.

The cover image is from Wood’s Animate Creation. The cover fonts are URW Typewriter and Guardian Sans. The text font is Adobe Minion Pro; the heading font is Adobe Myriad Condensed; and the code font is Dalton Maag’s Ubuntu Mono.