zoukankan      html  css  js  c++  java
  • 2、python全栈之路拾遗

    二、拾遗

    1、循环

    forwhile

    1.1 range

    range(0,10):正序,从下标0到下标9的范围

    range(10,-1,-1):倒序,从下标10到下标0

     

    1.2 break

    跳出本层循环

     

    1.3 continue

    跳出本次循环

     

    2else

    2.1 if中的else

    if xxx:

        pass

    else:

        pass

    当不满足if条件时,走else条件

    2.2 while中的else

    while True:

        pass

    else:

    pass

    True变为False时,走else条件

    2.3 for中的else条件

    当可迭代对象中的元素,被完整循环完毕后执行一次

    for item in xxx:

        pass

    else:

        # 当可迭代对象中的元素,被循环完毕后执行一次

        pass

    dic={
        'k1':'v1',
        'y2':'v1',
        'k11':'v1',
        'y3':'v1'
    }

    while True:
        n = 1
        for k in dic: # 'k1':'v1', #'y2':'v1', #'k11':'v1'
            if 'k' in k:
                del dic[k]
                break #break终止了循环,所以没有完整循环一遍
        else:
            # dic元素循环完毕
            break
    print(dic)

    3python2python3的区别

    3.1 输入

    raw_input()

    input()

    3.2 范围

    py3range()惰性运算,不打印不出来,py2中不打印也出来

    xrange()只在py2中有,和py3中的range()功能一样

    3.3 默认字符编码

    ascii(#-*-encoding:utf-8 -*-)

    utf-8

    3.4 输出

    print "alex"

    print('alex')

    3.5 除法

    /

    py3是精确到小数取整是//

    py2是整除

    4orand

    orand:判断顺序 只要or的第一个条件通过不会再判断or后面的条件

     

    5、运算符

    5.1 算数运算

     

    5.2 比较运算

     

    5.3 赋值运算

     

    5.4 逻辑运算

     

    5.5 成员运算

     

    5.6 is==的区别

    # is ==的区别

        # == 是判断值

        # is 是判断值和内存地址  身份运算

    6、例题

    有如下值集合 [11,22,33,44,55,66,77,88,99,90],将所有大于 66 的值保存至字典的第一个key 中,将小于 66 的值保存至第二个key 的值中。

    即: {'k1': 大于66 的所有值列表, 'k2': 小于66 的所有值列表}


    #方法一:
    dic = {'k1':[],'k2':[]}
    li = [11,22,33,44,55,66,77,88,99,90]
    for i in li:
        if i > 66:
            dic['k1'].append(i)
        else:
            dic['k2'].append(i)
    print(dic)

    #方法二:
    li = [11, 22, 33, 44, 55, 66, 77, 88, 99]
    dic = {}
    # dic = {'k1':[11,]}
    # dic = {'k1':[11,22,33,44,55],'k2': [77,88,99]}

    for item in li:
        if item < 66:
            # 11,22,33,44,55
            if 'k1' not in dic:
                dic['k1'] = [item, ]
            else:
                dic['k1'].append(item)
        elif item > 66:
            if 'k2' not in dic:
                dic['k2'] = [item, ]
            else:
                dic['k2'].append(item)
    print(dic)

  • 相关阅读:
    Codeforces Round #649 (Div. 2) D. Ehab's Last Corollary
    Educational Codeforces Round 89 (Rated for Div. 2) E. Two Arrays
    Educational Codeforces Round 89 (Rated for Div. 2) D. Two Divisors
    Codeforces Round #647 (Div. 2) E. Johnny and Grandmaster
    Codeforces Round #647 (Div. 2) F. Johnny and Megan's Necklace
    Codeforces Round #648 (Div. 2) G. Secure Password
    Codeforces Round #646 (Div. 2) F. Rotating Substrings
    C++STL常见用法
    各类学习慕课(不定期更新
    高阶等差数列
  • 原文地址:https://www.cnblogs.com/xiaojinyu/p/7464767.html
Copyright © 2011-2022 走看看