【Python编程练习100题】P11—P15

P11-怎样实现学生成绩排序

'''
学生成绩数据格式：
复杂列表，元素是字典或者元组
[
{'sno': 101, 'sname': "小张", 'sgrade': 88},
{'sno': 102, 'sname': "小王", 'sgrade': 77},
{'sno': 103, 'sname': "小李", 'sgrade': 99},
{'sno': 104, 'sname': "小赵", 'sgrade': 66}
]
'''
students = [
    {'sno': 101, 'sname': "小张", 'sgrade': 88},
    {'sno': 102, 'sname': "小王", 'sgrade': 77},
    {'sno': 103, 'sname': "小李", 'sgrade': 99},
    {'sno': 104, 'sname': "小赵", 'sgrade': 66}
]
students_sort1 = sorted(students, key = lambda x: x["sgrade"])
students_sort2 = sorted(students, key = lambda x: x["sgrade"], reverse = True)
print(f"sourse{students}\n, sort result1: {students_sort1}\n")
print(f"sourse{students}\n, sort result2: {students_sort2}\n")

sourse[{‘sno’: 101, ‘sname’: ‘小张’, ‘sgrade’: 88}, {‘sno’: 102, ‘sname’: ‘小王’, ‘sgrade’: 77}, {‘sno’: 103, ‘sname’: ‘小李’, ‘sgrade’: 99}, {‘sno’: 104, ‘sname’: ‘小赵’, ‘sgrade’: 66}]
, sort result1: [{‘sno’: 104, ‘sname’: ‘小赵’, ‘sgrade’: 66}, {‘sno’: 102, ‘sname’: ‘小王’, ‘sgrade’: 77}, {‘sno’: 101, ‘sname’: ‘小张’, ‘sgrade’: 88}, {‘sno’: 103, ‘sname’: ‘小李’, ‘sgrade’: 99}]

sourse[{‘sno’: 101, ‘sname’: ‘小张’, ‘sgrade’: 88}, {‘sno’: 102, ‘sname’: ‘小王’, ‘sgrade’: 77}, {‘sno’: 103, ‘sname’: ‘小李’, ‘sgrade’: 99}, {‘sno’: 104, ‘sname’: ‘小赵’, ‘sgrade’: 66}]
, sort result2: [{‘sno’: 103, ‘sname’: ‘小李’, ‘sgrade’: 99}, {‘sno’: 101, ‘sname’: ‘小张’, ‘sgrade’: 88}, {‘sno’: 102, ‘sname’: ‘小王’, ‘sgrade’: 77}, {‘sno’: 104, ‘sname’: ‘小赵’, ‘sgrade’: 66}]

P12-读取成绩文件排序的数据

'''
输入文件：
三列：学号、姓名、成绩
列之间用逗号分隔，比如"101,小张,88"
行之间用\n换行分割

处理：
读取文件，按成绩倒序排列

输出：
排序后的三列数据

'''

def read_file():
    result = []
    with open("./sort_grade_input.txt", encoding='utf-8') as fin:
        for line in fin:  # 遍历每一行
            line = line[:-1]  # 去掉末尾换行符
            result.append(line.split(","))  # 按照逗号分隔
    return result
        
def sort_grades(datas):
    return sorted(datas, 
                  key = lambda x : int(x[2]), # 第三列字符串转成int型再做比较
                  reverse = True)

def write_file(datas):
    with open("./sort_grade_output.txt", "w", encoding='utf-8') as fout:
        for data in datas:
            fout.write(",".join(data) + "\n")
    
# 读取文件
datas = read_file()
print("read_file datas:",datas)
# 排序数据
datas = sort_grades(datas)
print("sort_grades datas:",datas)
# 写出文件
write_file(datas)

read_file datas: [[‘101’, ‘小张’, ‘88’], [‘102’, ‘小王’, ‘77’], [‘103’, ‘小李’, ‘99’], [‘104’, ‘小赵’, ‘66’], [‘105’, ‘小强’, ‘55’]]
sort_grades datas: [[‘103’, ‘小李’, ‘99’], [‘101’, ‘小张’, ‘88’], [‘102’, ‘小王’, ‘77’], [‘104’, ‘小赵’, ‘66’], [‘105’, ‘小强’, ‘55’]]

P13-统计学生成绩高低平均分

'''
输入文件：
三列：学号、姓名、成绩
列之间用逗号分隔，比如"101,小张,88"
行之间用\n换行分割

输出：最高分、最低分、平均分

'''
import numpy as np

def compute_score():
    scores = []
    with open("./sort_grade_input.txt", encoding = 'utf-8',mode = 'r') as fin:
        for line in fin:  # 遍历每一行
            line = line[:-1]  # 去掉末尾换行符
            fields = line.split(",")  # 按照逗号分隔
            scores.append(int(fields[-1]))  # python中-1是最后一个位置，字符串转成数字
    max_score = max(scores)
    min_score = min(scores)
    avg_score = round(np.sum(scores) / len(scores), 2)  # 保留两位小数
    return max_score, min_score, avg_score      
            
    
max_score, min_score, avg_score = compute_score()
print(f"max_score = {max_score}, min_score = {min_score}, avg_score = {avg_score}")

max_score = 99, min_score = 55, avg_score = 77.0

P14-统计英文文章每个单词的出现次数

word_count = {}
with open("./Beginner Guide to Python.txt") as fin:
    for line in fin:  # 遍历每一行
        line = line[:-1]  # 去掉末尾换行符
        words = line.split( )  # 按照空格分隔
        for word in words:  #对于每个单词来说
            if word not in word_count:  #如果这个单词不在词典中
                word_count[word] = 0
            word_count[word] += 1

print(word_count)
print(
    sorted(
        word_count.items(),
        key = lambda x : x[1],
        reverse = True
    )[:10]  # 出现次数最多的前10个元素
)

[(‘Python’, 44), (‘to’, 34), (‘the’, 33), (‘a’, 28), (‘you’, 26), (‘and’, 24), (‘of’, 21), (‘for’, 19), (‘your’, 16), (‘can’, 10)]

P15 统计目录下的文件大小

import os
print(os.path.getsize("Beginner Guide to Python.txt")) # 单个文件大小

sum_size = 0
for file in os.listdir("."):  #列出目录下的所有文件（可能还会包含目录）
    if os.path.isfile(file):  # 过滤掉目录
        print(file)
        sum_size += os.path.getsize(file)  # 返回的是B
        
print("all size of dir: ", sum_size/1000)  # 除以1000变成KB，1kB = 1000B

6251
Beginner Guide to Python.txt
sort_grade_input.txt
sort_grade_output.txt
Untitled.ipynb
all size of dir: 33.56

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