Python 编程涉及到数值数据,这些数据可以存储在变量中,例如整数(如 10、-5、0)和浮点数(如 3.14、-0.5、2.0)。为了对这些数字执行计算,Python 提供了一套算术运算符。这些运算符就像计算器一样,是您在程序中执行数学任务的基本工具。基本算术运算Python 支持您熟悉的标准算术运算:加法 (+): 将两个数字相加。apples = 5 oranges = 10 total_fruit = apples + oranges print(total_fruit) # Output: 15 price = 9.99 tax = 0.80 total_cost = price + tax print(total_cost) # Output: 10.79减法 (-): 从第一个数字中减去第二个数字。budget = 100 spent = 35.50 remaining = budget - spent print(remaining) # Output: 64.5乘法 (*): 将两个数字相乘。width = 8 height = 12 area = width * height print(area) # Output: 96除法 (/): 用第一个数字除以第二个数字。需要注意的是,Python 中的标准除法总是产生一个浮点数,即使除法结果是整数。total_distance = 100 # kilometers time_hours = 2 # hours speed = total_distance / time_hours print(speed) # Output: 50.0 items = 10 people = 4 items_per_person = items / people print(items_per_person) # Output: 2.5请注意 100 / 2 的结果是 50.0,而不仅仅是 50。这种一致的行为有助于避免当您预期小数结果时可能出现的小问题。整数除法和取余Python 提供了另外两种专门的除法运算符,它们在处理整数时特别有用:整除 (//): 与标准 / 运算符一样执行除法,但它会丢弃小数部分,向下取整到最接近的整数。这也称为整数除法。cookies = 10 friends = 3 cookies_per_friend = cookies // friends print(cookies_per_friend) # Output: 3 (Each friend gets 3 whole cookies) value = 7 divisor = 2 result = value // divisor print(result) # Output: 3 (7 divided by 2 is 3.5, rounded down is 3) # Compare with standard division print(10 / 3) # Output: 3.3333333333333335 print(10 // 3) # Output: 3取余 (%): 此运算符不给出除法的结果,而是给出除法后剩余的余数。它通常被称为“余数运算符”。total_cookies = 10 friends = 3 leftover_cookies = total_cookies % friends print(leftover_cookies) # Output: 1 (After giving 3 cookies each, 1 is left) number = 17 divisor = 5 remainder = number % divisor print(remainder) # Output: 2 (17 divided by 5 is 3 with a remainder of 2)取余运算符常用于检查数字是偶数还是奇数。如果 number % 2 等于 0,则该数字为偶数,否则为奇数。num = 6 print(num % 2) # Output: 0 (So, 6 is even) num = 7 print(num % 2) # Output: 1 (So, 7 is odd)幂运算要将一个数字提高到另一个数字的幂,您可以使用双星号 (**) 运算符。幂运算 (**): 将第一个数字提高到第二个数字的幂。$x^{y}$ 写为 x ** y。base = 2 exponent = 3 power_result = base ** exponent # Equivalent to 2 * 2 * 2 print(power_result) # Output: 8 side = 5 area_square = side ** 2 # Equivalent to 5 * 5 (5 squared) print(area_square) # Output: 25运算顺序当一个表达式包含多个运算符时,Python 遵循标准的运算顺序,这与数学中的顺序相似(通常通过缩写词 PEMDAS/BODMAS 记忆:括号/方括号、指数/幂、乘法和除法、加法和减法)。括号 (): 括号内的运算首先执行。幂运算 **: 接下来执行。乘法 *、除法 /、整除 //、取余 %: 它们具有相同的优先级,从左到右计算。加法 +、减法 -: 它们具有相同的优先级,最后从左到右计算。请看这个例子:result = 2 + 3 * 4 print(result) # Output: 14 (Multiplication is done before addition: 2 + 12)如果您希望加法首先执行,请使用括号:result = (2 + 3) * 4 print(result) # Output: 20 (Parentheses force addition first: 5 * 4)另一个例子:calculation = 100 - 20 / 5 * 2 + 3**2 # Step-by-step evaluation: # 1. Exponentiation: 3**2 becomes 9 # Expression: 100 - 20 / 5 * 2 + 9 # 2. Division/Multiplication (from left to right): # 20 / 5 becomes 4.0 # Expression: 100 - 4.0 * 2 + 9 # 4.0 * 2 becomes 8.0 # Expression: 100 - 8.0 + 9 # 3. Addition/Subtraction (from left to right): # 100 - 8.0 becomes 92.0 # Expression: 92.0 + 9 # 92.0 + 9 becomes 101.0 print(calculation) # Output: 101.0使用括号可以使复杂的表达式更加清晰,即使根据优先级规则它们并非严格必要。当不确定时,使用括号来确保计算按照您预期的顺序进行。简写:增广赋值运算符在编程中,根据变量的当前值修改变量是非常常见的。例如,增加计数器或累加总和:count = 0 count = count + 1 # Increment count by 1 print(count) # Output: 1 total_cost = 50 item_price = 15.50 total_cost = total_cost + item_price # Add item_price to total_cost print(total_cost) # Output: 65.5Python 提供了简写运算符,称为增广赋值运算符,使这类操作更简洁:count = 0 count += 1 # Equivalent to count = count + 1 print(count) # Output: 1 score = 100 score -= 10 # Equivalent to score = score - 10 print(score) # Output: 90 multiplier = 5 multiplier *= 2 # Equivalent to multiplier = multiplier * 2 print(multiplier) # Output: 10 total = 50.0 total /= 4 # Equivalent to total = total / 4 print(total) # Output: 12.5这些简写运算符(+=、-=、*=、/=、//=、%=、**=)适用于所有算术运算符,并将操作与赋值结合起来。一旦您熟悉它们,它们很方便,并且通常使代码更容易阅读。您现在拥有在 Python 中执行各种计算的工具。通过结合变量、数值数据类型和这些算术运算符,您可以开始编写有效处理数字的程序。请记住,在需要时使用括号来阐明或控制运算顺序。