PyCharm 2024.1 Help

Examine suspended program

After the debugger session has started, the Debug tool window appears, and the program runs normally until one of the following happens:

After that, the program is suspended, allowing you to examine its current state, control its further execution, and test various scenarios at runtime.

Examine frames

The state of the program is represented by frames. When the program is suspended, the current frame stack is displayed on the Frames tab of the Debug tool window.

Frames tab of the Debug tool window

A frame corresponds to an active method or function call. It stores the local variables of the called method or function, its arguments, and the code context that enables expression evaluation.

Each time a method is called, a new frame is added to the top of the stack. When the execution of a method is complete, the corresponding frame is removed from the stack (in the last in, first out fashion).

Examining frames helps you understand why particular parameters were passed to a method and what the state of the caller was at the time of calling.

Copy stack to clipboard

  • To copy the call stack for the current thread, right-click anywhere on the Frames tab and select Copy Stack.

Examine/update variables

The Variables tab shows the list of the variables in the selected frame/thread. Examining the variables can help you understand why the program operates in a certain way.

The Variables tab shows you the variables visible from the current execution point

The icon on the left of each variable indicates its type.

Variable types

Icon

Description

An array

Local arrays

A primitive

Local primitive types

A watch

Watches and auto-variables.

A primitive

Local reference variables

Copy variables

When examining variables, you may need to copy a variable name or value to paste it somewhere else or compare it with another variable.

  • To copy the name of a variable, right-click the variable and select Copy Name.

  • To copy the value that a variable holds, right-click the variable and select Copy Value Ctrl+C.

  • By default, string variables are copied with single quotes. To change the quoting policy, click More More in the Debug tool window toolbar, select Debugger Settings | Variables Quoting Policy, and choose the required option.

    Changing variables quoting policy

Compare variables with clipboard

To compare a variable value with some other value, use the Compare Value with Clipboard option. This is helpful, for example, when a variable holds a long string, and you need to compare it with another long string.

  1. Copy the content you want to compare, for example, from a text file.

  2. In the Variables tab, right-click a variable and select Compare Value with Clipboard.

  3. Examine the differences in the Diff Viewer that opens. For more information about Diff Viewer, refer to Comparing Files and Folders.

View variables in a dedicated dialog

PyCharm allows you to inspect variables in a dedicated dialog. This is useful when you need to keep track of some variable (or the object whose reference it holds) and at the same time be able to navigate between frames and threads.

  • Right-click a variable or a watch and select Inspect.

    Inspect dialog

View data structures

  • When viewing variables in the Debug tool window, you can click View as Array, View as DataFrame, or View as Series links to display the data in the Data View tool window.

    Viewing data frames
  • By default, the new table representation is used. Click Switch Between Table Representations Switch Between Table Representations to change the table interface.

    Switching the table interface
  • Click Table Coloring Options Table Coloring Options to toggle and configure cell coloring .

    Switching the table interface

Set variable values

If you want to test how the program would behave with certain data or change its flow at runtime, you can achieve that by changing the variable values.

  1. Select a variable and press F2. Alternatively, select Set Value from the context menu.

  2. Enter the value for the variable and press Enter.

    Enter new value for the variable in the field right next to its name

You can navigate to declarations from the Variables pane.

  • To navigate to the code where the variable is declared, right-click the variable and select Jump to Source F4.

  • To navigate to the class declaration of the variable type, right-click the variable and select Jump to Type Source Shift+F4.

Evaluate expressions

PyCharm lets you evaluate expressions during a debugging session to obtain additional details about the program state or test various execution scenarios at runtime.

This feature only works if the program was suspended after hitting a breakpoint (not paused).

If there are breakpoints inside methods called within the expression, they will be ignored.

Evaluate a simple expression in the editor

To quickly evaluate an expression, point at it in the editor. Note that method calls cannot be evaluated this way.

  1. Point at the expression you want to evaluate. The result of the expression appears in a tooltip.

    Value tooltip
  2. To view child elements of the resulting object, click the Expand button or press Ctrl+F1.

    Value tooltip

If you find value tooltips distracting, you can increase the delay or disable them altogether. To do this, in the Settings dialog (Ctrl+Alt+S) , go to Build, Execution, Deployment | Debugger | Data Views and set the Show value tooltip and Value tooltip delay options according to your preference.

Evaluate a complex expression in the editor

If you want to evaluate an expression in the code that involves a method call, or you want to be specific about which portion of expression to evaluate, use the Quick Evaluate Expression option.

  1. Place the caret at the expression (to evaluate the closest matching expression) or select a portion of it (if you want to be specific about which part of a complex expression to evaluate).

  2. Click Run | Debugging Actions | Quick Evaluate Expression Ctrl+Alt+F8. Alternatively, hold Shift+Alt and click the selection.

    Value tooltip appears

You can configure Quick Evaluate Expression to work for a piece of code on just selecting it (without using the menu/shortcut). Use this option carefully, as you can accidentally call methods when it is enabled.

Evaluate expressions on selecting code

  • Go to Settings | Build, Execution, Deployment | Debugger | Data Views and set the Show value tooltip on code selection option.

Evaluate arbitrary expressions

Evaluating arbitrary expressions is the most flexible evaluating option. It lets you evaluate any custom code as long as it is in the context of the current frame. Using it, you can evaluate statements, function calls, loops, and so on.

  1. To evaluate an arbitrary expression, enter it in the Evaluate expression field in the Variables pane and press Enter

  2. The result is displayed right below. You can also add the expression to watches by clicking in the right-hand part of the expression field.

    Result of an expression in the Variables tab

If you want to evaluate long code blocks, you may want to use a dedicated dialog for that:

Evaluate expressions in a dedicated dialog

  1. If you want to start with some expression or a variable, which is currently in front of you (for example, in the editor or on the Variables pane), select it.

    Select the expression to start from
  2. Go to Run | Debugging Actions | Evaluate Expression Alt+F8 or select Evaluate Expression from the context menu. The shortcut may not work on Ubuntu (for correct operation, adjust the shortcut configuration).

  3. In the Evaluate dialog, modify the selected expression or enter a new one in the Expression field. Click Expand Shift+Enter to modify a multiline code fragment.

    The expression is entered in the Code Fragment field
  4. Click Evaluate (Ctrl+Enter for multiline mode). The expression result appears in the Result field.

    The result of the expression is taken from the return statement. When there is no return statement, the result is taken from the last line of code (it does not even have to be an expression: a single literal works too). When there is no valid line to take the value from, the result is undefined. If the specified expression cannot be evaluated, the Result field indicates the reason.

    Expression result is calculated

The Evaluate dialog is non-modal, so you can switch the focus back to the editor to copy other variables and expressions. You can also open multiple Evaluate dialogs.

View values inline

PyCharm shows the values of the variables right next to their usage.

Variable values are displayed at the lines where they are used

Once the variable value has changed, the inline view is updated with the new value and changes its color.

Inline values of the variables change with each step

If a line contains a reference to an object, you can examine its fields right in the editor. From this popup, you can also change the variable values and add inline watches.

Inline debugger hints

The inline view is enabled by default. To turn it off, in the Settings dialog (Ctrl+Alt+S) , go to Build, Execution, Deployment | Debugger | Data Views and disable the Show values inline option.

Add an Inline Watch

If you want the result of some expression to appear on a particular line, you can set up an inline watch for that. Inline watches are persistent and remain active after session restart.

  1. Click the inline hint referring to the object whose field you want to track.

  2. In the popup, select the field and click Add as Inline Watch.

    Adding an inline watch option
  3. Fine-tune the watch if needed. You can use any valid expression as a watch.

    Setting an inline watch
    Setting an inline watch

To remove an inline watch, hover over the watch and click the cross near it.

Watches

If you want to keep track of some variable or the result of a more complex expression, set up a watch for this variable or expression. This is useful when you need to evaluate something that is not regularly displayed on the list of variables, or to pin some instance variable thus eliminating the need to expand the tree after each step.

This feature only works if the program was suspended after hitting a breakpoint (not paused).

Watches are evaluated in the context of the selected frame. Watches cannot be evaluated when they are out of context or when they fail to compile. If this is the case, the watch is marked with the error icon Error icon.

Add a watch

  1. Click New Watch New Watch button on the Watches tab.

  2. Enter the variable or expression to be evaluated. In expressions, you can evaluate method calls, declare variables, and so on, as long as this is in the local context.

    Add watch

After you have added a variable/expression to Watches, it stays there and is evaluated for each step, providing you with the result in the current context.

Edit a watch

  • Right-click the desired watch and select Edit.

Copy a watch

  1. Select the watch you want to copy.

  2. Click Duplicate Watch Duplicate Watch button on the Variables/ Watches tab or press Ctrl+D.

Change the order of watches

For convenience, you can change the order in which the watches appear on the Variables/ Watches pane.

  • Use the Move Watch Up/Move Watch Down buttons on the Variables/ Watches pane or Ctrl+Up and Ctrl+Down keyboard shortcuts.

Delete a watch

  • To remove a single watch, right-click it and select Remove Watch. Alternatively, select the watch and press Delete on the Variables/ Watches pane.

  • To remove all watches, right-click anywhere on the Variables/ Watches pane and select Remove All Watches.

Watches allow for the same actions as variables do. For example, you can view them in a dedicated dialog or use them to navigate to the source code.

Watches are a part of your project. This means you can stop and rerun the debugging session without risk of losing them.

Execution point

Return to the current execution point

Examining the program state involves navigating in code, and you often need to return to the place where your program is suspended.

Do one of the following:

  • In the main menu, go to Run | Debugging Actions | Show Execution Point.

  • Press Alt+F10.

  • Click The Show Execution Point button on the stepping toolbar of the Debug tool window.

The current execution point is indicated with a blue line. The code at this line has not been executed yet.

Blue line indicating the current execution point
Last modified: 26 May 2024