python基础学习

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for、while、if

# for语法for<目标对象> in <对象集合>   if<条件1>：      语句块1      break;   if<条件1>：      语句块1      contine   语句块3else    语句块4

while 循环条件:    循环内容

if x<0:    print(x,'负数')elif x==0:    print(x,'为零')elif x==1:    print(x,'为一')else:    print(x,'为>1的值')

List列表

#list声明list1=["a","b","c"]list2=[1,2,3,4]list3=[[1,2,3,4],["a","b","c"]]list4=[(1,2,3,4),("a","b","c")]list5=[(1,2,3,4),["a","b","c"]]#List中的索引与切片#索引  和java一样list1[0]list1[3]list1[-1]list1[-3]#切片  [起:止] 止不包括list1[0:2]list1[0:-1]list1[-3:-1]#list追加list1.append("watermelon")#list添加list1.insert(0,"grapeful")#list的移除list1.remove("apple")#删除list中的最后一个元素  即后进先出list1.pop()

字典

#创建diet={"a":"apple","b":"banana","p":"pear"}#数字做键diet={1:"apple",2:"banana",3:"pear"}#字典的修改  删除diet[1]='great apple'del diet[1]#更快创建方式diet={}diet=diet.fromkeys(("a","b","c"),"apple")#查询diet={"a":"apple","b":"banana","c":"pear"}print("b" in diet)#循环print(len(diet))print(diet.keys())print(diet.values())print(diet.items())print(iter(diet))ite=iter(diet)for k in ite:    print(k)

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