1. if语句
Python的常规if语法:
if 布尔判断1:
表达式1
elif 布尔判断2:
表达式2
elif 布尔判断3:
表达式3
…
elif 布尔判断N:
表达式N
else:
else表达式
下面给出非常简单的实例:
y = 2000
if y < 1000:
print("small")
elif y < 10000:
print("medium")
else:
print("large")
输出结果:
False
x is nonzero value
medium
2. while语句
while语句用于0次或者多次执行某个表达式,循环之行的次数取决于while循环中布尔表达式的状态。
x = 0
while x < 5:
print("pass")
x += 1
输出结果:
pass
pass
pass
pass
pass
我们还可以结合if语句,做另一个判断然后,利用break语句提前跳出while循环
x = 0
while x < 5:
print("pass")
x += 1
if x == 3:
print("Not Pass")
break
输出结果:
pass
pass
pass
Not Pass
3. for…in语句
Python 的for语句重用了关键字in。与while循环类似,for循环也支持break以及continue语句,也包含可选的else分支。变量将逐一引用可迭代量中的每一个对象,可迭代量可以是任何数据类型。如:
for country in ["Denmark", "Finland", "Norway", "Sweden"]:
print(country)
输出结果:
Denmark
Finland
Norway
Sweden
for letter in "ABCDEFGHIJKLMNOPQRSTUVWXYZ":
if letter in "AEIOU":
print(letter, "is a vowel")
else:
print(letter, "is a consonant")
输出结果:
A is a vowel
B is a consonant
C is a consonant
D is a consonant
E is a vowel
F is a consonant
G is a consonant
H is a consonant
I is a vowel
J is a consonant
K is a consonant
L is a consonant
M is a consonant
N is a consonant
O is a vowel
P is a consonant
Q is a consonant
R is a consonant
S is a consonant
T is a consonant
U is a vowel
V is a consonant
W is a consonant
X is a consonant
Y is a consonant
Z is a consonant
NEXT。。。
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