Python入门系列（五）一篇搞懂python语句

If语句

elif关键字是pythons表示“如果前面的条件不为真，那么试试这个条件”。

The else keyword catches anything which isn't caught by the preceding conditions.

a = 200
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")
else:
  print("a is greater than b")

如果只有一条语句要执行，则可以将其与If语句放在同一行。

if a > b: print("a is greater than b")

如果只有一条语句要执行，一条用于If，另一条用于else，则可以将所有语句放在同一行中

a = 2
b = 330
print("A") if a > b else print("B")

and关键字是一个逻辑运算符，用于组合条件语句

a = 200
b = 33
c = 500
if a > b and c > a:
  print("Both conditions are True")

or关键字是一个逻辑运算符，用于组合条件语句

a = 200
b = 33
c = 500
if a > b or a > c:
  print("At least one of the conditions is True")

循环语言

while语句

使用while循环，只要条件为true，我们就可以执行一组语句。

i = 1
while i < 6:
  print(i)
  i += 1

使用break语句，即使while条件为true，我们也可以停止循环

i = 1
while i < 6:
  print(i)
  if i == 3:
    break
  i += 1

使用continue语句，我们可以停止当前迭代，然后继续下一个迭代

i = 0
while i < 6:
  i += 1
  if i == 3:
    continue
  print(i)

使用else语句，当条件不再为真时，我们可以运行一段代码

i = 1
while i < 6:
  print(i)
  i += 1
else:
  print("i is no longer less than 6")

for语句

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x)

for循环中的else关键字指定循环完成时要执行的代码块

for x in range(6):
  print(x)
else:
  print("Finally finished!")

for x in range(6):
  if x == 3: break
  print(x)
else:
  print("Finally finished!")

#If the loop breaks, the else block is not executed.

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