Python列表遍历与索引操作详解

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在"列表遍历 - hard_real-time_computing_systems"章节中,作者深入探讨了如何在Python编程中有效地处理列表。首先,介绍的是基本的for循环遍历列表的方法,这是最常用的迭代方式。通过`for cheese in cheeses:`这样的结构,代码会逐个取出列表`cheeses`中的元素,并执行相应的操作。这种方式适用于只需读取元素的情况。 然而,当需要修改列表中的元素时,就需要借助索引访问。这里介绍了一种结合`range()`和`len()`的技巧,如`for i in range(len(numbers)):`,通过`i`作为索引,能够实现按顺序访问并更新列表`numbers`中的元素。值得注意的是,对于空列表,`for`循环内部的代码块不会被执行。 此外,章节还提到列表嵌套的处理,虽然它们在内部被视为单个元素,但可以通过多层for循环或递归来访问其中的子列表。如果遇到`IndexError`,通常是由于尝试访问超出列表范围的索引,需要确保循环变量的边界条件正确。 《Think Python》这本书强调了像计算机科学家一样思考问题,包括用形式化的语言表示思想,设计并平衡解决方案,以及通过观察和实验验证假设。在这个章节中,读者学习了如何通过编程实现这些概念,特别是与列表操作相关的逻辑和注意事项。掌握列表遍历技巧是理解和应用Python编程基础的关键,对于提升问题求解能力至关重要。

R R version 4.2.2 (2022-10-31) -- "Innocent and Trusting" Copyright (C) 2022 The R Foundation for Statistical Computing Platform: x86_64-conda-linux-gnu (64-bit) R is free software and comes with ABSOLUTELY NO WARRANTY. You are welcome to redistribute it under certain conditions. Type 'license()' or 'licence()' for distribution details. Natural language support but running in an English locale R is a collaborative project with many contributors.Type 'contributors()' for more information and 'citation()' on how to cite R or R packages in publications. Type 'demo()' for some demos, 'help()' for on-line help, or 'help.start()' for an HTML browser interface to help. Type 'q()' to quit R. library(ape) setwd("/ifs1/User/dengwei/NTF_data/7.14/rooted_species_tree") species_tree <- read.tree("species_tree.treefile")> compare_trees <- function(gene_tree_file, species_tree) { gene_tree <- read.tree(gene_tree_file) diff_count <- comparePhylo(gene_tree, species_tree, force.rooted = TRUE) return(diff_count) } batch_compare_trees <- function(gene_tree_folder, species_tree) { gene_tree_files <- list.files(path = gene_tree_folder, pattern = ".treefile", full.names = TRUE) diff_counts <- data.frame(Gene_Tree_File = gene_tree_files, Diff_Count = numeric(length(gene_tree_files)), stringsAsFactors = FALSE) for (i in seq_along(gene_tree_files)) { gene_tree_file <- gene_tree_files[i] diff_counts$Diff_Count[i] <- compare_trees(gene_tree_file, species_tree) } return(diff_counts) } gene_tree_folder <- "/ifs1/User/dengwei/NTF_data/7.14/rooted_gene_tree" diff_counts <- batch_compare_trees(gene_tree_folder, species_tree) Error in if (n1 == n2) paste("Both trees have the same number of tips:", : the condition has length > 1

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