python基础(变量、基础数据类型、流程控制)

今日内容html {overflow-x: initial !important;}:root { --bg-color:#ffffff; --text-color:#333333; --select-text-bg-color:#B5D6FC; --select-text-font-color:auto; --monospace:"Lucida Console",Consolas,"Courier",monospace; }
html { font-size: 14px; background-color: var(--bg-color); color: var(--text-color); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; -webkit-font-smoothing: antialiased; }
body { margin: 0px; padding: 0px; height: auto; bottom: 0px; top: 0px; left: 0px; right: 0px; font-size: 1rem; line-height: 1.42857; overflow-x: hidden; background: inherit; tab-size: 4; }
iframe { margin: auto; }
a.url { word-break: break-all; }
a:active, a:hover { outline: 0px; }
.in-text-selection, ::selection { text-shadow: none; background: var(--select-text-bg-color); color: var(--select-text-font-color); }
#write { margin: 0px auto; height: auto; width: inherit; word-break: normal; overflow-wrap: break-word; position: relative; white-space: normal; overflow-x: visible; padding-top: 40px; }
#write.first-line-indent p { text-indent: 2em; }
#write.first-line-indent li p, #write.first-line-indent p * { text-indent: 0px; }
#write.first-line-indent li { margin-left: 2em; }
.for-image #write { padding-left: 8px; padding-right: 8px; }
body.typora-export { padding-left: 30px; padding-right: 30px; }
.typora-export .footnote-line, .typora-export li, .typora-export p { white-space: pre-wrap; }
@media screen and (max-width: 500px) {
body.typora-export { padding-left: 0px; padding-right: 0px; }
#write { padding-left: 20px; padding-right: 20px; }
.CodeMirror-sizer { margin-left: 0px !important; }
.CodeMirror-gutters { display: none !important; }
}
#write li > figure:last-child { margin-bottom: 0.5rem; }
#write ol, #write ul { position: relative; }
img { max-width: 100%; vertical-align: middle; }
button, input, select, textarea { color: inherit; font: inherit; }
input[type="checkbox"], input[type="radio"] { line-height: normal; padding: 0px; }
*, ::after, ::before { box-sizing: border-box; }
#write h1, #write h2, #write h3, #write h4, #write h5, #write h6, #write p, #write pre { width: inherit; }
#write h1, #write h2, #write h3, #write h4, #write h5, #write h6, #write p { position: relative; }
p { line-height: inherit; }
h1, h2, h3, h4, h5, h6 { break-after: avoid-page; break-inside: avoid; orphans: 2; }
p { orphans: 4; }
h1 { font-size: 2rem; }
h2 { font-size: 1.8rem; }
h3 { font-size: 1.6rem; }
h4 { font-size: 1.4rem; }
h5 { font-size: 1.2rem; }
h6 { font-size: 1rem; }
.md-math-block, .md-rawblock, h1, h2, h3, h4, h5, h6, p { margin-top: 1rem; margin-bottom: 1rem; }
.hidden { display: none; }
.md-blockmeta { color: rgb(204, 204, 204); font-weight: 700; font-style: italic; }
a { cursor: pointer; }
sup.md-footnote { padding: 2px 4px; background-color: rgba(238, 238, 238, 0.7); color: rgb(85, 85, 85); border-radius: 4px; cursor: pointer; }
sup.md-footnote a, sup.md-footnote a:hover { color: inherit; text-transform: inherit; text-decoration: inherit; }
#write input[type="checkbox"] { cursor: pointer; width: inherit; height: inherit; }
figure { overflow-x: auto; margin: 1.2em 0px; max-width: calc(100% + 16px); padding: 0px; }
figure > table { margin: 0px !important; }
tr { break-inside: avoid; break-after: auto; }
thead { display: table-header-group; }
table { border-collapse: collapse; border-spacing: 0px; width: 100%; overflow: auto; break-inside: auto; text-align: left; }
table.md-table td { min-width: 32px; }
.CodeMirror-gutters { border-right: 0px; background-color: inherit; }
.CodeMirror-linenumber { user-select: none; }
.CodeMirror { text-align: left; }
.CodeMirror-placeholder { opacity: 0.3; }
.CodeMirror pre { padding: 0px 4px; }
.CodeMirror-lines { padding: 0px; }
div.hr:focus { cursor: none; }
#write pre { white-space: pre-wrap; }
#write.fences-no-line-wrapping pre { white-space: pre; }
#write pre.ty-contain-cm { white-space: normal; }
.CodeMirror-gutters { margin-right: 4px; }
.md-fences { font-size: 0.9rem; display: block; break-inside: avoid; text-align: left; overflow: visible; white-space: pre; background: inherit; position: relative !important; }
.md-diagram-panel { width: 100%; margin-top: 10px; text-align: center; padding-top: 0px; padding-bottom: 8px; overflow-x: auto; }
#write .md-fences.mock-cm { white-space: pre-wrap; }
.md-fences.md-fences-with-lineno { padding-left: 0px; }
#write.fences-no-line-wrapping .md-fences.mock-cm { white-space: pre; overflow-x: auto; }
.md-fences.mock-cm.md-fences-with-lineno { padding-left: 8px; }
.CodeMirror-line, twitterwidget { break-inside: avoid; }
.footnotes { opacity: 0.8; font-size: 0.9rem; margin-top: 1em; margin-bottom: 1em; }
.footnotes + .footnotes { margin-top: 0px; }
.md-reset { margin: 0px; padding: 0px; border: 0px; outline: 0px; vertical-align: top; background: 0px 0px; text-decoration: none; text-shadow: none; float: none; position: static; width: auto; height: auto; white-space: nowrap; cursor: inherit; -webkit-tap-highlight-color: transparent; line-height: normal; font-weight: 400; text-align: left; box-sizing: content-box; direction: ltr; }
li div { padding-top: 0px; }
blockquote { margin: 1rem 0px; }
li .mathjax-block, li p { margin: 0.5rem 0px; }
li { margin: 0px; position: relative; }
blockquote > :last-child { margin-bottom: 0px; }
blockquote > :first-child, li > :first-child { margin-top: 0px; }
.footnotes-area { color: rgb(136, 136, 136); margin-top: 0.714rem; padding-bottom: 0.143rem; white-space: normal; }
#write .footnote-line { white-space: pre-wrap; }
@media print {
body, html { border: 1px solid transparent; height: 99%; break-after: avoid; break-before: avoid; }
#write { margin-top: 0px; padding-top: 0px; border-color: transparent !important; }
.typora-export * { -webkit-print-color-adjust: exact; }
html.blink-to-pdf { font-size: 13px; }
.typora-export #write { padding-left: 32px; padding-right: 32px; padding-bottom: 0px; break-after: avoid; }
.typora-export #write::after { height: 0px; }
}
.footnote-line { margin-top: 0.714em; font-size: 0.7em; }
a img, img a { cursor: pointer; }
pre.md-meta-block { font-size: 0.8rem; min-height: 0.8rem; white-space: pre-wrap; background: rgb(204, 204, 204); display: block; overflow-x: hidden; }
p > .md-image:only-child:not(.md-img-error) img, p > img:only-child { display: block; margin: auto; }
p > .md-image:only-child { display: inline-block; width: 100%; }
#write .MathJax_Display { margin: 0.8em 0px 0px; }
.md-math-block { width: 100%; }
.md-math-block:not(:empty)::after { display: none; }
[contenteditable="true"]:active, [contenteditable="true"]:focus { outline: 0px; box-shadow: none; }
.md-task-list-item { position: relative; list-style-type: none; }
.task-list-item.md-task-list-item { padding-left: 0px; }
.md-task-list-item > input { position: absolute; top: 0px; left: 0px; margin-left: -1.2em; margin-top: calc(1em - 10px); border: none; }
.math { font-size: 1rem; }
.md-toc { min-height: 3.58rem; position: relative; font-size: 0.9rem; border-radius: 10px; }
.md-toc-content { position: relative; margin-left: 0px; }
.md-toc-content::after, .md-toc::after { display: none; }
.md-toc-item { display: block; color: rgb(65, 131, 196); }
.md-toc-item a { text-decoration: none; }
.md-toc-inner:hover { text-decoration: underline; }
.md-toc-inner { display: inline-block; cursor: pointer; }
.md-toc-h1 .md-toc-inner { margin-left: 0px; font-weight: 700; }
.md-toc-h2 .md-toc-inner { margin-left: 2em; }
.md-toc-h3 .md-toc-inner { margin-left: 4em; }
.md-toc-h4 .md-toc-inner { margin-left: 6em; }
.md-toc-h5 .md-toc-inner { margin-left: 8em; }
.md-toc-h6 .md-toc-inner { margin-left: 10em; }
@media screen and (max-width: 48em) {
.md-toc-h3 .md-toc-inner { margin-left: 3.5em; }
.md-toc-h4 .md-toc-inner { margin-left: 5em; }
.md-toc-h5 .md-toc-inner { margin-left: 6.5em; }
.md-toc-h6 .md-toc-inner { margin-left: 8em; }
}
a.md-toc-inner { font-size: inherit; font-style: inherit; font-weight: inherit; line-height: inherit; }
.footnote-line a:not(.reversefootnote) { color: inherit; }
.md-attr { display: none; }
.md-fn-count::after { content: "."; }
code, pre, samp, tt { font-family: var(--monospace); }
kbd { margin: 0px 0.1em; padding: 0.1em 0.6em; font-size: 0.8em; color: rgb(36, 39, 41); background: rgb(255, 255, 255); border: 1px solid rgb(173, 179, 185); border-radius: 3px; box-shadow: rgba(12, 13, 14, 0.2) 0px 1px 0px, rgb(255, 255, 255) 0px 0px 0px 2px inset; white-space: nowrap; vertical-align: middle; }
.md-comment { color: rgb(162, 127, 3); opacity: 0.8; font-family: var(--monospace); }
code { text-align: left; vertical-align: initial; }
a.md-print-anchor { white-space: pre !important; border-width: initial !important; border-style: none !important; border-color: initial !important; display: inline-block !important; position: absolute !important; width: 1px !important; right: 0px !important; outline: 0px !important; background: 0px 0px !important; text-decoration: initial !important; text-shadow: initial !important; }
.md-inline-math .MathJax_SVG .noError { display: none !important; }
.html-for-mac .inline-math-svg .MathJax_SVG { vertical-align: 0.2px; }
.md-math-block .MathJax_SVG_Display { text-align: center; margin: 0px; position: relative; text-indent: 0px; max-width: none; max-height: none; min-height: 0px; min-width: 100%; width: auto; overflow-y: hidden; display: block !important; }
.MathJax_SVG_Display, .md-inline-math .MathJax_SVG_Display { width: auto; margin: inherit; display: inline-block !important; }
.MathJax_SVG .MJX-monospace { font-family: var(--monospace); }
.MathJax_SVG .MJX-sans-serif { font-family: sans-serif; }
.MathJax_SVG { display: inline; font-style: normal; font-weight: 400; line-height: normal; zoom: 90%; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; }
.MathJax_SVG * { transition: none 0s ease 0s; }
.MathJax_SVG_Display svg { vertical-align: middle !important; margin-bottom: 0px !important; margin-top: 0px !important; }
.os-windows.monocolor-emoji .md-emoji { font-family: "Segoe UI Symbol", sans-serif; }
.md-diagram-panel > svg { max-width: 100%; }
[lang="mermaid"] svg, [lang="flow"] svg { max-width: 100%; height: auto; }
[lang="mermaid"] .node text { font-size: 1rem; }
table tr th { border-bottom: 0px; }
video { max-width: 100%; display: block; margin: 0px auto; }
iframe { max-width: 100%; width: 100%; border: none; }
.highlight td, .highlight tr { border: 0px; }

html { font-size: 19px; }
html, body { margin: auto; background: rgb(254, 254, 254); }
body { font-family: Vollkorn, Palatino, Times; color: rgb(51, 51, 51); line-height: 1.4; text-align: justify; }
#write { max-width: 960px; margin: 0px auto 2em; line-height: 1.53; padding-top: 40px; }
#write > h1:first-child, h1 { margin-top: 1.6em; font-weight: normal; }
h1 { font-size: 3em; }
h2 { margin-top: 2em; font-weight: normal; }
h3 { font-weight: normal; font-style: italic; margin-top: 3em; }
h1, h2, h3 { text-align: center; }
h2::after { border-bottom: 1px solid rgb(47, 47, 47); content: ""; width: 100px; display: block; margin: 0px auto; height: 1px; }
h1 + h2, h2 + h3 { margin-top: 0.83em; }
p, .mathjax-block { margin-top: 0px; }
ul { list-style: square; padding-left: 1.2em; }
ol { padding-left: 1.2em; }
blockquote { margin-left: 1em; padding-left: 1em; border-left: 1px solid rgb(221, 221, 221); }
code, pre { font-family: Consolas, Menlo, Monaco, monospace, serif; font-size: 0.9em; background: white; }
.md-fences { margin-left: 1em; padding-left: 1em; border: 1px solid rgb(221, 221, 221); padding-bottom: 8px; padding-top: 6px; margin-bottom: 1.5em; }
a { color: rgb(36, 132, 193); text-decoration: none; }
a:hover { text-decoration: underline; }
a img { border: none; }
h1 a, h1 a:hover { color: rgb(51, 51, 51); text-decoration: none; }
hr { color: rgb(221, 221, 221); height: 1px; margin: 2em 0px; border-top: 1px solid rgb(221, 221, 221); border-bottom: none; border-left: 0px; border-right: 0px; }
.ty-table-edit { background: rgb(237, 237, 237); padding-top: 4px; }
table { margin-bottom: 1.33333rem; }
table th, table td { padding: 8px; line-height: 1.33333rem; vertical-align: top; border-top: 1px solid rgb(221, 221, 221); }
table th { font-weight: bold; }
table thead th { vertical-align: bottom; }
table caption + thead tr:first-child th, table caption + thead tr:first-child td, table colgroup + thead tr:first-child th, table colgroup + thead tr:first-child td, table thead:first-child tr:first-child th, table thead:first-child tr:first-child td { border-top: 0px; }
table tbody + tbody { border-top: 2px solid rgb(221, 221, 221); }
.task-list { padding: 0px; }
.md-task-list-item { padding-left: 1.6rem; }
.md-task-list-item > input::before { content: "√"; display: inline-block; width: 1.33333rem; height: 1.6rem; vertical-align: middle; text-align: center; color: rgb(221, 221, 221); background-color: rgb(254, 254, 254); }
.md-task-list-item > input:checked::before, .md-task-list-item > input[checked]::before { color: inherit; }
.md-tag { color: inherit; font: inherit; }
#write pre.md-meta-block { min-height: 35px; padding: 0.5em 1em; }
#write pre.md-meta-block { white-space: pre; background: rgb(248, 248, 248); border-width: 0px 30px; border-top-style: initial; border-bottom-style: initial; border-top-color: initial; border-bottom-color: initial; border-image: initial; color: rgb(153, 153, 153); width: 100vw; max-width: calc(100% + 60px); margin-left: -30px; border-left-style: solid; border-left-color: rgb(248, 248, 248); border-right-style: solid; border-right-color: rgb(248, 248, 248); margin-bottom: 2em; margin-top: -1.33333rem; padding-top: 26px; padding-bottom: 10px; line-height: 1.8em; font-size: 0.76em; padding-left: 0px; }
.md-img-error.md-image > .md-meta { vertical-align: bottom; }
#write > h5.md-focus::before { top: 2px; }
.md-toc { margin-top: 40px; }
.md-toc-content { padding-bottom: 20px; }
.outline-expander::before { color: inherit; font-size: 14px; top: auto; content: ""; font-family: FontAwesome; }
.outline-expander:hover::before, .outline-item-open > .outline-item > .outline-expander::before { content: ""; }
#typora-source { font-family: Courier, monospace; color: rgb(106, 106, 106); }
.html-for-mac #typora-sidebar { box-shadow: rgba(0, 0, 0, 0.176) 0px 6px 12px; }
.cm-s-typora-default .cm-header, .cm-s-typora-default .cm-property, .CodeMirror.cm-s-typora-default div.CodeMirror-cursor { color: rgb(66, 139, 202); }
.cm-s-typora-default .cm-atom, .cm-s-typora-default .cm-number { color: rgb(119, 119, 119); }
.typora-node .file-list-item-parent-loc, .typora-node .file-list-item-time, .typora-node .file-list-item-summary { font-family: arial, sans-serif; }
.md-task-list-item > input { margin-left: -1.3em; margin-top: calc(1rem - 12px); }
.md-mathjax-midline { background: rgb(250, 250, 250); }
.md-fences .code-tooltip { bottom: -2em !important; }
.dropdown-menu .divider { border-color: rgb(229, 229, 229); }

今日内容

变量

  • 定义:将程序运行中的中间值临时存储起来,以便再次使用

  • 变量一般用于后期开发使用

  • 变量名使用规范:

    1. 数字、字母、下划线组成

    2. 不能以数字开头

    3. 禁止使用python关键字

      ['False', 'None', 'True', 'and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

    4. 变量名要具有可描述性

    5. 变量名要区分大小写

    6. 变量名不能使用拼音和中文

    7. 推荐写法

      7.1驼峰体

      Alexdfkasd = "adsdf"

      7.2下划线

      alex_name = "asdfasdf"

常量及注释

常量

  • 定义:变量名大写就是常量

  • 注意:其他语言中常量不能被修改,python中的常量可以被修改,但是一般不要修改

  • 常量一般用于文件配置

注释

  • 定义:给一些晦涩难懂的代码进行注释

  • 单行注释:# 注释后的代码不会被执行,且不占内存

  • 多行注释:''' '''或”“” “”“可以换行

  • PEP8开发规范:代码不宜过长,超过界面分界线

基础数据类型

int整型

  • 用于计算和比较:+、-、*、/、

str字符串

“ ”

‘ ’

“‘ ”’

bool布尔值

True False

str(int)时字符串内容只能是数字

python2和python3的区别

  • python2

    • 源码不统一
    • 代码有重复
    • print不用加括号
    • 做除法时,输出为整数
    • raw_input获取到全为字符串,input获取到什么类型,输出就是什么类型
  • python3

    • 代码统一
    • 代码没有重复
    • print要加括号
    • 做除法时,输出是浮点型
    • input获取到的全为字符串

流程控制语句

  • if嵌套

    • 如果 条件:

      缩进 结果

      缩进 如果 条件:

      缩进 结果

      用于判断

  • if else 二选一

    • 如果 条件:

    • 缩进 结果

      否则:

      缩进 结果

  • if elif elif elif 多选一或零

    • 如果 条件:

      缩进 结果

      在如果 条件:

      缩进 结果

      在如果 条件:

      缩进 结果

上一篇:MyBatis-plus 代码生成器


下一篇:Go语言 数据类型,流程控制