Walmart said a weak global economy is battering its shoppers. “The retail environment remains challenging in the US and our international markets,’’ chief financial officer Charles Holley said. Net income rose 1.3 percent to $4.07 billion, missing estimates. Sales rose 2.4 percent to $116.2 billion. Walmart now expects sales to rise 2 to 3 percent for the full year; its previous forecast was 5 to 6 percent. The company also took a dime per share off its full-year profit outlook, cutting it to between $5.10 and $5.30.