字符编码ASCII （ord(‘字符’)获取ASCII表中对应的十进制数字，反过来使用chr获取字符）

# 1.生成0~9字符串
# print(ord("0"), ord("9"))
a = ""
for v in range(ord("0"), ord("9") + 1):
    # print(v)
    a += chr(v)
print(a)

# 2.生成a~z字符串
# print(ord("a"), ord("z"))
b = ""
for v in range(ord('a'), ord('z') + 1):
    b += chr(v)
print(b)

# 3.生成A~Z字符串
# print(ord("A"), ord("Z"))
c = ""
for v in range(ord("A"), ord("Z") + 1):
    c += chr(v)
print(c)

# 4.生成0~9a~zA~Z字符串
print(a + b + c)