1.概述
只需要掌握is, is not, not, if,for, while的用法，就可以很轻松的实现python中所有的判断语句，循环语句。
2.is, is not, not
在python中 None, False, 空字符串"", 0, 空列表[], 空字典{}, 空元组()都相当于False,可以用 is 或者 is not 来准确区分它们
a = ""if a is not None:
print('not None')if a is not False:
print('not false')if a is not {}:
print('not {}')如果用not来计算的话，他们都是Ｆalse
if not a:
print("not a")3.in
可用于字符串，列表元素，字典键值判断。
a = "shanghai"my_lists = list(a)
my_dic = {"a":1,"b":2,"c":3}print(a)print(my_lists)if "s" in a: print("s in a")if "a" in my_lists: print("a in my list")if "a" in my_dic: print("a in my dic")4.if
可实现选择逻辑，三目运算
#ifa = ""if a is None:
print("None")elif a is False:
print("False")else:
print("else")#三目运算print('True') if a is "" else 'False'5.for,while
continue，这次循环到此结束，开始执行下个循环。
break，整个循环都结束了。
else，是当整个循环都结束后，才执行。如果提前结束，则不执行。
#forfor i in range(10): #continue
print(i) if i == 9: breakelse: print('the laste one is :%s'%i)#whilesum10 = 0
i = 1while i <= 10:
i += 1 #continue
sum10 += i #breakelse: print(sum10)
作者：Godric_wsw
链接：https://www.jianshu.com/p/1a851d1a84fd
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